diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/ConnectionPersistenceActor.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/ConnectionPersistenceActor.java
index afc86845df..e1d3dc8ddf 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/ConnectionPersistenceActor.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/ConnectionPersistenceActor.java
@@ -116,8 +116,8 @@
  * remote server is delegated to a child actor that uses a specific client (AMQP 1.0 or 0.9.1).
  */
 public final class ConnectionPersistenceActor
-        extends AbstractShardedPersistenceActor<ConnectivityCommand, Connection, ConnectionId, ConnectionState,
-        ConnectivityEvent> {
+        extends AbstractShardedPersistenceActor<ConnectivityCommand<?>, Connection, ConnectionId, ConnectionState,
+        ConnectivityEvent<?>> {
 
     /**
      * Prefix to prepend to the connection ID to construct the persistence ID.
@@ -254,7 +254,7 @@ public String snapshotPluginId() {
     }
 
     @Override
-    protected Class<ConnectivityEvent> getEventClass() {
+    protected Class<?> getEventClass() {
         return ConnectivityEvent.class;
     }
 
@@ -274,7 +274,7 @@ protected ConnectionDeletedStrategies getDeletedStrategy() {
     }
 
     @Override
-    protected EventStrategy<ConnectivityEvent, Connection> getEventStrategy() {
+    protected EventStrategy<ConnectivityEvent<?>, Connection> getEventStrategy() {
         return ConnectionEventStrategies.getInstance();
     }
 
@@ -295,12 +295,12 @@ protected boolean entityExistsAsDeleted() {
     }
 
     @Override
-    protected DittoRuntimeExceptionBuilder newNotAccessibleExceptionBuilder() {
+    protected DittoRuntimeExceptionBuilder<?> newNotAccessibleExceptionBuilder() {
         return ConnectionNotAccessibleException.newBuilder(entityId);
     }
 
     @Override
-    protected void publishEvent(final ConnectivityEvent event) {
+    protected void publishEvent(final ConnectivityEvent<?> event) {
         // Do nothing because nobody subscribes for connectivity events.
     }
 
@@ -341,8 +341,8 @@ protected void recoveryCompleted(final RecoveryCompleted event) {
     }
 
     @Override
-    public void onMutation(final Command command, final ConnectivityEvent event, final WithDittoHeaders response,
-            final boolean becomeCreated, final boolean becomeDeleted) {
+    public void onMutation(final Command<?> command, final ConnectivityEvent<?> event,
+            final WithDittoHeaders<?> response, final boolean becomeCreated, final boolean becomeDeleted) {
         if (command instanceof StagedCommand) {
             interpretStagedCommand(((StagedCommand) command).withSenderUnlessDefined(getSender()));
         } else {
@@ -381,9 +381,7 @@ private void interpretStagedCommand(final StagedCommand command) {
                 interpretStagedCommand(command.next());
                 break;
             case PERSIST_AND_APPLY_EVENT:
-                persistAndApplyEvent(command.getEvent(), (event, connection) -> {
-                    interpretStagedCommand(command.next());
-                });
+                persistAndApplyEvent(command.getEvent(), (event, connection) -> interpretStagedCommand(command.next()));
                 break;
             case SEND_RESPONSE:
                 command.getSender().tell(command.getResponse(), getSelf());
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/stages/StagedCommand.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/stages/StagedCommand.java
index cd15ca94d5..3d53e37cbf 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/stages/StagedCommand.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/stages/StagedCommand.java
@@ -42,18 +42,18 @@
  */
 public final class StagedCommand implements ConnectivityCommand<StagedCommand>, Iterator<StagedCommand> {
 
-    private static final ConnectivityEvent DUMMY_EVENT =
+    private static final ConnectivityEvent<?> DUMMY_EVENT =
             ConnectionClosed.of(ConnectionId.dummy(), DittoHeaders.empty());
 
-    private final ConnectivityCommand command;
-    private final ConnectivityEvent event;
-    private final WithDittoHeaders response;
+    private final ConnectivityCommand<?> command;
+    private final ConnectivityEvent<?> event;
+    private final WithDittoHeaders<?> response;
     private final ActorRef sender;
     private final Collection<ConnectionAction> actions;
 
-    private StagedCommand(final ConnectivityCommand command,
-            final ConnectivityEvent event,
-            final WithDittoHeaders response,
+    private StagedCommand(final ConnectivityCommand<?> command,
+            final ConnectivityEvent<?> event,
+            final WithDittoHeaders<?> response,
             final ActorRef sender,
             final Collection<ConnectionAction> actions) {
         this.command = command;
@@ -72,36 +72,36 @@ private StagedCommand(final ConnectivityCommand command,
      * @param actions remaining actions.
      * @return the staged command.
      */
-    public static StagedCommand of(final ConnectivityCommand command, final ConnectivityEvent event,
-            final WithDittoHeaders response, final List<ConnectionAction> actions) {
+    public static StagedCommand of(final ConnectivityCommand<?> command, final ConnectivityEvent<?> event,
+            final WithDittoHeaders<?> response, final List<ConnectionAction> actions) {
         return new StagedCommand(command, event, response, ActorRef.noSender(), actions);
     }
 
     /**
      * @return a dummy placeholder event.
      */
-    public static ConnectivityEvent dummyEvent() {
+    public static ConnectivityEvent<?> dummyEvent() {
         return DUMMY_EVENT;
     }
 
     /**
      * @return the wrapped command.
      */
-    public ConnectivityCommand getCommand() {
+    public ConnectivityCommand<?> getCommand() {
         return command;
     }
 
     /**
      * @return the event to persist, apply or publish.
      */
-    public ConnectivityEvent getEvent() {
+    public ConnectivityEvent<?> getEvent() {
         return event;
     }
 
     /**
      * @return the response to send to the original sender, or the signal to forward to client actors.
      */
-    public WithDittoHeaders getResponse() {
+    public WithDittoHeaders<?> getResponse() {
         return response;
     }
 
@@ -132,7 +132,7 @@ public StagedCommand withSenderUnlessDefined(final ActorRef newSender) {
      * @param response the response.
      * @return the copy.
      */
-    public StagedCommand withResponse(final WithDittoHeaders response) {
+    public StagedCommand withResponse(final WithDittoHeaders<?> response) {
         return new StagedCommand(command, event, response, sender, actions);
     }
 
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/AbstractConnectivityCommandStrategy.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/AbstractConnectivityCommandStrategy.java
index b36a8f378d..722818bffa 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/AbstractConnectivityCommandStrategy.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/AbstractConnectivityCommandStrategy.java
@@ -35,8 +35,8 @@
  *
  * @param <C> the type of the handled command
  */
-abstract class AbstractConnectivityCommandStrategy<C extends ConnectivityCommand>
-        extends AbstractCommandStrategy<C, Connection, ConnectionState, Result<ConnectivityEvent>> {
+abstract class AbstractConnectivityCommandStrategy<C extends ConnectivityCommand<?>>
+        extends AbstractCommandStrategy<C, Connection, ConnectionState, Result<ConnectivityEvent<?>>> {
 
     AbstractConnectivityCommandStrategy(final Class<C> theMatchingClass) {
         super(theMatchingClass);
@@ -54,14 +54,14 @@ protected Optional<Metadata> calculateRelativeMetadata(@Nullable final Connectio
     }
 
     ConnectionNotAccessibleException notAccessible(final Context<ConnectionState> context,
-            final WithDittoHeaders command) {
+            final WithDittoHeaders<?> command) {
         return ConnectionNotAccessibleException.newBuilder(context.getState().id())
                 .dittoHeaders(command.getDittoHeaders())
                 .build();
     }
 
     static Optional<DittoRuntimeException> validate(final Context<ConnectionState> context,
-            final ConnectivityCommand command, final Connection connection) {
+            final ConnectivityCommand<?> command, final Connection connection) {
         try {
             context.getState().getValidator().accept(command, () -> connection);
             return Optional.empty();
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/AbstractEphemeralStrategy.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/AbstractEphemeralStrategy.java
index d3f38b3870..b435c5df85 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/AbstractEphemeralStrategy.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/AbstractEphemeralStrategy.java
@@ -34,26 +34,27 @@
  *
  * @param <C> the type of the handled command
  */
-abstract class AbstractEphemeralStrategy<C extends ConnectivityCommand> extends AbstractConnectivityCommandStrategy<C> {
+abstract class AbstractEphemeralStrategy<C extends ConnectivityCommand<?>>
+        extends AbstractConnectivityCommandStrategy<C> {
 
 
     AbstractEphemeralStrategy(final Class<C> theMatchingClass) {
         super(theMatchingClass);
     }
 
-    abstract WithDittoHeaders getResponse(final ConnectionState connectionId, final DittoHeaders headers);
+    abstract WithDittoHeaders<?> getResponse(final ConnectionState connectionId, final DittoHeaders headers);
 
     abstract List<ConnectionAction> getActions();
 
     @Override
-    protected Result<ConnectivityEvent> doApply(final Context<ConnectionState> context,
+    protected Result<ConnectivityEvent<?>> doApply(final Context<ConnectionState> context,
             @Nullable final Connection connection,
             final long nextRevision,
             final C command,
             @Nullable final Metadata metadata) {
 
-        final ConnectivityEvent event = StagedCommand.dummyEvent();
-        final WithDittoHeaders response = getResponse(context.getState(), command.getDittoHeaders());
+        final ConnectivityEvent<?> event = StagedCommand.dummyEvent();
+        final WithDittoHeaders<?> response = getResponse(context.getState(), command.getDittoHeaders());
         final List<ConnectionAction> actions = getActions();
         return newMutationResult(StagedCommand.of(command, event, response, actions), event, response);
     }
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/AbstractSingleActionStrategy.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/AbstractSingleActionStrategy.java
index 25392b1ea4..a887d7b4b8 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/AbstractSingleActionStrategy.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/AbstractSingleActionStrategy.java
@@ -33,7 +33,7 @@
  *
  * @param <C> the type of the handled command
  */
-abstract class AbstractSingleActionStrategy<C extends ConnectivityCommand>
+abstract class AbstractSingleActionStrategy<C extends ConnectivityCommand<?>>
         extends AbstractConnectivityCommandStrategy<C> {
 
     AbstractSingleActionStrategy(final Class<C> theMatchingClass) {
@@ -46,13 +46,13 @@ abstract class AbstractSingleActionStrategy<C extends ConnectivityCommand>
     abstract ConnectionAction getAction();
 
     @Override
-    protected Result<ConnectivityEvent> doApply(final Context<ConnectionState> context,
+    protected Result<ConnectivityEvent<?>> doApply(final Context<ConnectionState> context,
             @Nullable final Connection connection,
             final long nextRevision,
             final C command,
             @Nullable final Metadata metadata) {
 
-        final ConnectivityEvent event = StagedCommand.dummyEvent();
+        final ConnectivityEvent<?> event = StagedCommand.dummyEvent();
         final List<ConnectionAction> actions = Collections.singletonList(getAction());
         return newMutationResult(StagedCommand.of(command, event, command, actions), event, command);
     }
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/CloseConnectionStrategy.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/CloseConnectionStrategy.java
index 70226f9ba2..f957d9cee8 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/CloseConnectionStrategy.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/CloseConnectionStrategy.java
@@ -46,7 +46,7 @@ final class CloseConnectionStrategy extends AbstractConnectivityCommandStrategy<
     }
 
     @Override
-    protected Result<ConnectivityEvent> doApply(final Context<ConnectionState> context,
+    protected Result<ConnectivityEvent<?>> doApply(final Context<ConnectionState> context,
             @Nullable final Connection connection,
             final long nextRevision,
             final CloseConnection command,
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ConnectionConflictStrategy.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ConnectionConflictStrategy.java
index 349c13a2ae..039afd9b33 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ConnectionConflictStrategy.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ConnectionConflictStrategy.java
@@ -35,7 +35,7 @@ final class ConnectionConflictStrategy extends AbstractConnectivityCommandStrate
     }
 
     @Override
-    protected Result<ConnectivityEvent> doApply(final Context<ConnectionState> context,
+    protected Result<ConnectivityEvent<?>> doApply(final Context<ConnectionState> context,
             @Nullable final Connection entity,
             final long nextRevision,
             final CreateConnection command,
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ConnectionCreatedStrategies.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ConnectionCreatedStrategies.java
index 87de2db2a2..254fd78615 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ConnectionCreatedStrategies.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ConnectionCreatedStrategies.java
@@ -27,7 +27,8 @@
  * Strategies to handle signals as an existing connection.
  */
 public class ConnectionCreatedStrategies
-        extends AbstractCommandStrategies<ConnectivityCommand, Connection, ConnectionState, Result<ConnectivityEvent>> {
+        extends
+        AbstractCommandStrategies<ConnectivityCommand<?>, Connection, ConnectionState, Result<ConnectivityEvent<?>>> {
 
     private static final ConnectionCreatedStrategies CREATED_STRATEGIES = newCreatedStrategies();
 
@@ -63,16 +64,16 @@ private static ConnectionCreatedStrategies newCreatedStrategies() {
     }
 
     @Override
-    public boolean isDefined(final ConnectivityCommand command) {
+    public boolean isDefined(final ConnectivityCommand<?> command) {
         // always defined so as to forward signals.
         return true;
     }
 
     @Override
-    public Result<ConnectivityEvent> unhandled(final Context<ConnectionState> context,
+    public Result<ConnectivityEvent<?>> unhandled(final Context<ConnectionState> context,
             @Nullable final Connection entity,
             final long nextRevision,
-            final ConnectivityCommand command) {
+            final ConnectivityCommand<?> command) {
 
         return ResultFactory.newErrorResult(ConnectionNotAccessibleException
                 .newBuilder(context.getState().id())
@@ -81,7 +82,7 @@ public Result<ConnectivityEvent> unhandled(final Context<ConnectionState> contex
     }
 
     @Override
-    protected Result<ConnectivityEvent> getEmptyResult() {
+    protected Result<ConnectivityEvent<?>> getEmptyResult() {
         return ResultFactory.emptyResult();
     }
 
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ConnectionDeletedStrategies.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ConnectionDeletedStrategies.java
index 8a43facf27..2771625425 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ConnectionDeletedStrategies.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ConnectionDeletedStrategies.java
@@ -27,7 +27,8 @@
  * Strategies to handle signals as a nonexistent connection.
  */
 public class ConnectionDeletedStrategies
-        extends AbstractCommandStrategies<ConnectivityCommand, Connection, ConnectionState, Result<ConnectivityEvent>> {
+        extends
+        AbstractCommandStrategies<ConnectivityCommand<?>, Connection, ConnectionState, Result<ConnectivityEvent<?>>> {
 
     private static final ConnectionDeletedStrategies DELETED_STRATEGIES = newDeletedStrategies();
 
@@ -51,10 +52,10 @@ private static ConnectionDeletedStrategies newDeletedStrategies() {
     }
 
     @Override
-    public Result<ConnectivityEvent> unhandled(final Context<ConnectionState> context,
+    public Result<ConnectivityEvent<?>> unhandled(final Context<ConnectionState> context,
             @Nullable final Connection entity,
             final long nextRevision,
-            final ConnectivityCommand command) {
+            final ConnectivityCommand<?> command) {
 
         context.getLog().withCorrelationId(command)
                 .warning("Received command for deleted connection, rejecting: <{}>", command);
@@ -64,13 +65,13 @@ public Result<ConnectivityEvent> unhandled(final Context<ConnectionState> contex
     }
 
     @Override
-    public boolean isDefined(final ConnectivityCommand command) {
+    public boolean isDefined(final ConnectivityCommand<?> command) {
         // always defined so as to log ignored signals on debug level.
         return true;
     }
 
     @Override
-    protected Result<ConnectivityEvent> getEmptyResult() {
+    protected Result<ConnectivityEvent<?>> getEmptyResult() {
         return ResultFactory.emptyResult();
     }
 
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/CreateConnectionStrategy.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/CreateConnectionStrategy.java
index bfdaf3f54c..b1ded045d5 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/CreateConnectionStrategy.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/CreateConnectionStrategy.java
@@ -51,7 +51,7 @@ final class CreateConnectionStrategy extends AbstractConnectivityCommandStrategy
     }
 
     @Override
-    protected Result<ConnectivityEvent> doApply(final Context<ConnectionState> context,
+    protected Result<ConnectivityEvent<?>> doApply(final Context<ConnectionState> context,
             @Nullable final Connection entity,
             final long nextRevision,
             final CreateConnection command,
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/DeleteConnectionStrategy.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/DeleteConnectionStrategy.java
index a5b6da2207..72c8a25b72 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/DeleteConnectionStrategy.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/DeleteConnectionStrategy.java
@@ -47,7 +47,7 @@ final class DeleteConnectionStrategy extends AbstractConnectivityCommandStrategy
     }
 
     @Override
-    protected Result<ConnectivityEvent> doApply(final Context<ConnectionState> context,
+    protected Result<ConnectivityEvent<?>> doApply(final Context<ConnectionState> context,
             @Nullable final Connection connection,
             final long nextRevision,
             final DeleteConnection command,
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ModifyConnectionStrategy.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ModifyConnectionStrategy.java
index b1f0dbd6cf..d3088febf1 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ModifyConnectionStrategy.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/ModifyConnectionStrategy.java
@@ -54,7 +54,7 @@ final class ModifyConnectionStrategy extends AbstractConnectivityCommandStrategy
     }
 
     @Override
-    protected Result<ConnectivityEvent> doApply(final Context<ConnectionState> context,
+    protected Result<ConnectivityEvent<?>> doApply(final Context<ConnectionState> context,
             @Nullable final Connection entity,
             final long nextRevision,
             final ModifyConnection command,
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/OpenConnectionStrategy.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/OpenConnectionStrategy.java
index 2b3fd1efdf..890eca1f11 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/OpenConnectionStrategy.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/OpenConnectionStrategy.java
@@ -48,7 +48,7 @@ final class OpenConnectionStrategy extends AbstractConnectivityCommandStrategy<O
     }
 
     @Override
-    protected Result<ConnectivityEvent> doApply(final Context<ConnectionState> context,
+    protected Result<ConnectivityEvent<?>> doApply(final Context<ConnectionState> context,
             @Nullable final Connection connection,
             final long nextRevision,
             final OpenConnection command,
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/RetrieveConnectionStrategy.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/RetrieveConnectionStrategy.java
index d8bb7c4d2b..10c178870c 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/RetrieveConnectionStrategy.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/RetrieveConnectionStrategy.java
@@ -33,7 +33,7 @@ final class RetrieveConnectionStrategy extends AbstractConnectivityCommandStrate
     }
 
     @Override
-    protected Result<ConnectivityEvent> doApply(final Context<ConnectionState> context,
+    protected Result<ConnectivityEvent<?>> doApply(final Context<ConnectionState> context,
             @Nullable final Connection entity,
             final long nextRevision,
             final RetrieveConnection command,
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/StagedCommandStrategy.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/StagedCommandStrategy.java
index 5d354f9cac..3dfa365efa 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/StagedCommandStrategy.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/StagedCommandStrategy.java
@@ -33,7 +33,7 @@ final class StagedCommandStrategy extends AbstractConnectivityCommandStrategy<St
     }
 
     @Override
-    protected Result<ConnectivityEvent> doApply(final Context<ConnectionState> context,
+    protected Result<ConnectivityEvent<?>> doApply(final Context<ConnectionState> context,
             @Nullable final Connection entity,
             final long nextRevision,
             final StagedCommand command,
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/TestConnectionConflictStrategy.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/TestConnectionConflictStrategy.java
index a4700cd672..d45cb3e240 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/TestConnectionConflictStrategy.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/TestConnectionConflictStrategy.java
@@ -35,7 +35,7 @@ final class TestConnectionConflictStrategy extends AbstractConnectivityCommandSt
     }
 
     @Override
-    protected Result<ConnectivityEvent> doApply(final Context<ConnectionState> context,
+    protected Result<ConnectivityEvent<?>> doApply(final Context<ConnectionState> context,
             @Nullable final Connection entity,
             final long nextRevision,
             final TestConnection command,
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/TestConnectionStrategy.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/TestConnectionStrategy.java
index e71ed7e2c6..a85ce36d5c 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/TestConnectionStrategy.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/commands/TestConnectionStrategy.java
@@ -48,7 +48,7 @@ final class TestConnectionStrategy extends AbstractConnectivityCommandStrategy<T
     }
 
     @Override
-    protected Result<ConnectivityEvent> doApply(final Context<ConnectionState> context,
+    protected Result<ConnectivityEvent<?>> doApply(final Context<ConnectionState> context,
             @Nullable final Connection entity,
             final long nextRevision,
             final TestConnection command,
diff --git a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/events/ConnectionEventStrategies.java b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/events/ConnectionEventStrategies.java
index 01c44ada84..e2edfbcd39 100644
--- a/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/events/ConnectionEventStrategies.java
+++ b/services/connectivity/messaging/src/main/java/org/eclipse/ditto/services/connectivity/messaging/persistence/strategies/events/ConnectionEventStrategies.java
@@ -24,7 +24,7 @@
 /**
  * Strategies to modify a connection by events.
  */
-public final class ConnectionEventStrategies extends AbstractEventStrategies<ConnectivityEvent, Connection> {
+public final class ConnectionEventStrategies extends AbstractEventStrategies<ConnectivityEvent<?>, Connection> {
 
     private static final ConnectionEventStrategies INSTANCE = new ConnectionEventStrategies();
 
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/PolicyPersistenceActor.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/PolicyPersistenceActor.java
index 838fc8ac0e..0bbf295c07 100755
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/PolicyPersistenceActor.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/PolicyPersistenceActor.java
@@ -64,7 +64,7 @@
  * PersistentActor which "knows" the state of a single {@link Policy}.
  */
 public final class PolicyPersistenceActor
-        extends AbstractShardedPersistenceActor<Command, Policy, PolicyId, PolicyId, PolicyEvent> {
+        extends AbstractShardedPersistenceActor<Command<?>, Policy, PolicyId, PolicyId, PolicyEvent<?>> {
 
     /**
      * The prefix of the persistenceId for Policies.
@@ -128,7 +128,7 @@ public String snapshotPluginId() {
     }
 
     @Override
-    protected Class<PolicyEvent> getEventClass() {
+    protected Class<?> getEventClass() {
         return PolicyEvent.class;
     }
 
@@ -143,12 +143,12 @@ protected PolicyCommandStrategies getCreatedStrategy() {
     }
 
     @Override
-    protected CommandStrategy<? extends Command, Policy, PolicyId, Result<PolicyEvent>> getDeletedStrategy() {
+    protected CommandStrategy<? extends Command<?>, Policy, PolicyId, Result<PolicyEvent<?>>> getDeletedStrategy() {
         return PolicyCommandStrategies.getCreatePolicyStrategy(policyConfig);
     }
 
     @Override
-    protected EventStrategy<PolicyEvent, Policy> getEventStrategy() {
+    protected EventStrategy<PolicyEvent<?>, Policy> getEventStrategy() {
         return PolicyEventStrategies.getInstance();
     }
 
@@ -168,12 +168,12 @@ protected boolean entityExistsAsDeleted() {
     }
 
     @Override
-    protected DittoRuntimeExceptionBuilder newNotAccessibleExceptionBuilder() {
+    protected DittoRuntimeExceptionBuilder<?> newNotAccessibleExceptionBuilder() {
         return PolicyNotAccessibleException.newBuilder(entityId);
     }
 
     @Override
-    protected void publishEvent(final PolicyEvent event) {
+    protected void publishEvent(final PolicyEvent<?> event) {
         pubSubMediator.tell(DistPubSubAccess.publishViaGroup(PolicyEvent.TYPE_PREFIX, event), getSender());
 
         final boolean policyEnforcerInvalidatedPreemptively = Boolean.parseBoolean(event.getDittoHeaders()
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/AbstractPolicyCommandStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/AbstractPolicyCommandStrategy.java
index d925bafb32..efca2f0e5e 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/AbstractPolicyCommandStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/AbstractPolicyCommandStrategy.java
@@ -60,7 +60,7 @@
  * {@link org.eclipse.ditto.services.models.policies.commands.sudo.SudoCommand} are handled which are no PolicyCommands.
  */
 abstract class AbstractPolicyCommandStrategy<C extends Command<C>>
-        extends AbstractConditionHeaderCheckingCommandStrategy<C, Policy, PolicyId, PolicyEvent> {
+        extends AbstractConditionHeaderCheckingCommandStrategy<C, Policy, PolicyId, PolicyEvent<?>> {
 
     static SubjectType TOKEN_INTEGRATION = PoliciesModelFactory.newSubjectType("actions/activateTokenIntegration");
 
@@ -239,7 +239,7 @@ protected SubjectExpiry roundPolicySubjectExpiry(final SubjectExpiry expiry) {
      * @param command the command which caused the change of the policy entries.
      * @return an Optional with ErrorResponse if a subject was invalid, an empty Optional if everything was valid.
      */
-    protected static Optional<Result<PolicyEvent>> checkForAlreadyExpiredSubject(final Iterable<PolicyEntry> entries,
+    protected static Optional<Result<PolicyEvent<?>>> checkForAlreadyExpiredSubject(final Iterable<PolicyEntry> entries,
             final DittoHeaders dittoHeaders, final Command<?> command) {
 
         return StreamSupport.stream(entries.spliterator(), false)
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ActivateSubjectStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ActivateSubjectStrategy.java
index fb291a219f..0950daa192 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ActivateSubjectStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ActivateSubjectStrategy.java
@@ -50,7 +50,7 @@ final class ActivateSubjectStrategy extends AbstractPolicyCommandStrategy<Activa
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final ActivateSubject command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ActivateSubjectsStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ActivateSubjectsStrategy.java
index dcd7a2aa9a..d47c115c1a 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ActivateSubjectsStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ActivateSubjectsStrategy.java
@@ -55,7 +55,7 @@ final class ActivateSubjectsStrategy extends AbstractPolicyCommandStrategy<Activ
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final ActivateSubjects command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/CreatePolicyStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/CreatePolicyStrategy.java
index 2aeb9d4c14..d1d1f2f183 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/CreatePolicyStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/CreatePolicyStrategy.java
@@ -48,7 +48,7 @@ final class CreatePolicyStrategy extends AbstractPolicyCommandStrategy<CreatePol
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy entity,
             final long nextRevision,
             final CreatePolicy command,
@@ -69,7 +69,7 @@ protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
         }
         final Policy newPolicyWithLifecycle = newPolicyBuilder.build();
 
-        final Optional<Result<PolicyEvent>> alreadyExpiredSubject =
+        final Optional<Result<PolicyEvent<?>>> alreadyExpiredSubject =
                 checkForAlreadyExpiredSubject(newPolicyWithLifecycle, dittoHeaders, command);
         if (alreadyExpiredSubject.isPresent()) {
             return alreadyExpiredSubject.get();
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeletePolicyEntryStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeletePolicyEntryStrategy.java
index 8d8d32f312..d338f659a9 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeletePolicyEntryStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeletePolicyEntryStrategy.java
@@ -45,7 +45,7 @@ final class DeletePolicyEntryStrategy extends AbstractPolicyCommandStrategy<Dele
 
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final DeletePolicyEntry command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeletePolicyStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeletePolicyStrategy.java
index 5b295435c1..f9e4ff2d7b 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeletePolicyStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeletePolicyStrategy.java
@@ -40,7 +40,7 @@ final class DeletePolicyStrategy extends AbstractPolicyCommandStrategy<DeletePol
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy entity,
             final long nextRevision,
             final DeletePolicy command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeleteResourceStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeleteResourceStrategy.java
index fb27315ab7..8fb4c7fb62 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeleteResourceStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeleteResourceStrategy.java
@@ -46,7 +46,7 @@ final class DeleteResourceStrategy extends AbstractPolicyCommandStrategy<DeleteR
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final DeleteResource command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeleteSubjectStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeleteSubjectStrategy.java
index 5e317362c2..560725e4e7 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeleteSubjectStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/DeleteSubjectStrategy.java
@@ -46,7 +46,7 @@ final class DeleteSubjectStrategy extends AbstractPolicyCommandStrategy<DeleteSu
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final DeleteSubject command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyPolicyEntriesStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyPolicyEntriesStrategy.java
index e86ecd1a39..333b5ca7cd 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyPolicyEntriesStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyPolicyEntriesStrategy.java
@@ -53,7 +53,7 @@ final class ModifyPolicyEntriesStrategy extends AbstractPolicyCommandStrategy<Mo
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy entity,
             final long nextRevision,
             final ModifyPolicyEntries command,
@@ -79,7 +79,7 @@ protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
         final ModifyPolicyEntries adjustedCommand = ModifyPolicyEntries.of(command.getEntityId(), adjustedEntries,
                 dittoHeaders);
 
-        final Optional<Result<PolicyEvent>> alreadyExpiredSubject =
+        final Optional<Result<PolicyEvent<?>>> alreadyExpiredSubject =
                 checkForAlreadyExpiredSubject(policyEntries, dittoHeaders, command);
         if (alreadyExpiredSubject.isPresent()) {
             return alreadyExpiredSubject.get();
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyPolicyEntryStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyPolicyEntryStrategy.java
index de4674b608..4ca16dba44 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyPolicyEntryStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyPolicyEntryStrategy.java
@@ -51,7 +51,7 @@ final class ModifyPolicyEntryStrategy extends AbstractPolicyCommandStrategy<Modi
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final ModifyPolicyEntry command,
@@ -90,7 +90,7 @@ protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
                 dittoHeaders);
         final Policy newPolicy = nonNullPolicy.setEntry(adjustedPolicyEntry);
 
-        final Optional<Result<PolicyEvent>> alreadyExpiredSubject =
+        final Optional<Result<PolicyEvent<?>>> alreadyExpiredSubject =
                 checkForAlreadyExpiredSubject(newPolicy, dittoHeaders, command);
         if (alreadyExpiredSubject.isPresent()) {
             return alreadyExpiredSubject.get();
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyPolicyStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyPolicyStrategy.java
index 196c408d76..490f81de7e 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyPolicyStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyPolicyStrategy.java
@@ -49,7 +49,7 @@ final class ModifyPolicyStrategy extends AbstractPolicyCommandStrategy<ModifyPol
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy entity,
             final long nextRevision,
             final ModifyPolicy command,
@@ -79,7 +79,7 @@ protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
             return ResultFactory.newErrorResult(e, adjustedCommand);
         }
 
-        final Optional<Result<PolicyEvent>> alreadyExpiredSubject =
+        final Optional<Result<PolicyEvent<?>>> alreadyExpiredSubject =
                 checkForAlreadyExpiredSubject(modifiedPolicyWithImplicits, dittoHeaders, command);
         if (alreadyExpiredSubject.isPresent()) {
             return alreadyExpiredSubject.get();
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyResourceStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyResourceStrategy.java
index ca5e354fa4..f71b0c1c4f 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyResourceStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyResourceStrategy.java
@@ -46,7 +46,7 @@ final class ModifyResourceStrategy extends AbstractPolicyCommandStrategy<ModifyR
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final ModifyResource command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyResourcesStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyResourcesStrategy.java
index 3704b7819e..551140db21 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyResourcesStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifyResourcesStrategy.java
@@ -53,7 +53,7 @@ final class ModifyResourcesStrategy extends AbstractPolicyCommandStrategy<Modify
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final ModifyResources command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifySubjectStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifySubjectStrategy.java
index b12b5ed511..541eeae69c 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifySubjectStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifySubjectStrategy.java
@@ -46,7 +46,7 @@ final class ModifySubjectStrategy extends AbstractPolicyCommandStrategy<ModifySu
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final ModifySubject command,
@@ -67,7 +67,7 @@ protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
 
             final Policy newPolicy = nonNullPolicy.setSubjectFor(label, adjustedSubject);
 
-            final Optional<Result<PolicyEvent>> alreadyExpiredSubject =
+            final Optional<Result<PolicyEvent<?>>> alreadyExpiredSubject =
                     checkForAlreadyExpiredSubject(newPolicy, dittoHeaders, command);
             if (alreadyExpiredSubject.isPresent()) {
                 return alreadyExpiredSubject.get();
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifySubjectsStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifySubjectsStrategy.java
index dde7434098..75a8118ccc 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifySubjectsStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/ModifySubjectsStrategy.java
@@ -50,7 +50,7 @@ final class ModifySubjectsStrategy extends AbstractPolicyCommandStrategy<ModifyS
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final ModifySubjects command,
@@ -69,7 +69,7 @@ protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
 
             final Policy newPolicy = nonNullPolicy.setSubjectsFor(label, adjustedSubjects);
 
-            final Optional<Result<PolicyEvent>> alreadyExpiredSubject =
+            final Optional<Result<PolicyEvent<?>>> alreadyExpiredSubject =
                     checkForAlreadyExpiredSubject(newPolicy, dittoHeaders, command);
             if (alreadyExpiredSubject.isPresent()) {
                 return alreadyExpiredSubject.get();
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/PolicyCommandStrategies.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/PolicyCommandStrategies.java
index bdb3acfecc..cbdffc3ff3 100755
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/PolicyCommandStrategies.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/PolicyCommandStrategies.java
@@ -29,7 +29,7 @@
  * Command strategies of {@code PolicyPersistenceActor}.
  */
 public final class PolicyCommandStrategies
-        extends AbstractCommandStrategies<Command, Policy, PolicyId, Result<PolicyEvent>> {
+        extends AbstractCommandStrategies<Command<?>, Policy, PolicyId, Result<PolicyEvent<?>>> {
 
     @Nullable private static volatile PolicyCommandStrategies instance;
     @Nullable private static volatile CreatePolicyStrategy createPolicyStrategy;
@@ -94,7 +94,7 @@ public static PolicyCommandStrategies getInstance(final PolicyConfig policyConfi
      * @param policyConfig the PolicyConfig of the Policy service to apply.
      * @return command strategy to create a policy.
      */
-    public static CommandStrategy<CreatePolicy, Policy, PolicyId, Result<PolicyEvent>> getCreatePolicyStrategy(
+    public static CommandStrategy<CreatePolicy, Policy, PolicyId, Result<PolicyEvent<?>>> getCreatePolicyStrategy(
             final PolicyConfig policyConfig) {
         CreatePolicyStrategy localCreatePolicyStrategy = createPolicyStrategy;
         if (null == localCreatePolicyStrategy) {
@@ -109,7 +109,7 @@ public static CommandStrategy<CreatePolicy, Policy, PolicyId, Result<PolicyEvent
     }
 
     @Override
-    protected Result<PolicyEvent> getEmptyResult() {
+    protected Result<PolicyEvent<?>> getEmptyResult() {
         return ResultFactory.emptyResult();
     }
 
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/PolicyConflictStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/PolicyConflictStrategy.java
index b3dca71907..f45111e13c 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/PolicyConflictStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/PolicyConflictStrategy.java
@@ -38,7 +38,7 @@ final class PolicyConflictStrategy extends AbstractPolicyCommandStrategy<CreateP
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy entity,
             final long nextRevision,
             final CreatePolicy command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrievePolicyEntriesStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrievePolicyEntriesStrategy.java
index c9576f4b81..5ab4b1affc 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrievePolicyEntriesStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrievePolicyEntriesStrategy.java
@@ -39,7 +39,7 @@ final class RetrievePolicyEntriesStrategy extends
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final RetrievePolicyEntries command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrievePolicyEntryStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrievePolicyEntryStrategy.java
index a9db250a41..26fd3e9d50 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrievePolicyEntryStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrievePolicyEntryStrategy.java
@@ -40,7 +40,7 @@ final class RetrievePolicyEntryStrategy extends
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final RetrievePolicyEntry command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrievePolicyStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrievePolicyStrategy.java
index 7e9bc9229e..13cc5f9db9 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrievePolicyStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrievePolicyStrategy.java
@@ -37,7 +37,7 @@ final class RetrievePolicyStrategy extends AbstractPolicyQueryCommandStrategy<Re
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy entity,
             final long nextRevision,
             final RetrievePolicy command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveResourceStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveResourceStrategy.java
index e8e9582359..38c6d9fed3 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveResourceStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveResourceStrategy.java
@@ -41,7 +41,7 @@ final class RetrieveResourceStrategy extends AbstractPolicyQueryCommandStrategy<
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final RetrieveResource command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveResourcesStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveResourcesStrategy.java
index d71401e4ae..c371765b65 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveResourcesStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveResourcesStrategy.java
@@ -41,7 +41,7 @@ final class RetrieveResourcesStrategy extends AbstractPolicyQueryCommandStrategy
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final RetrieveResources command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveSubjectStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveSubjectStrategy.java
index 490a644f7d..cd1b71ff62 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveSubjectStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveSubjectStrategy.java
@@ -43,7 +43,7 @@ final class RetrieveSubjectStrategy extends AbstractPolicyQueryCommandStrategy<R
 
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final RetrieveSubject command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveSubjectsStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveSubjectsStrategy.java
index d6dc607bad..e5dca0c881 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveSubjectsStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/RetrieveSubjectsStrategy.java
@@ -41,7 +41,7 @@ final class RetrieveSubjectsStrategy extends AbstractPolicyQueryCommandStrategy<
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy policy,
             final long nextRevision,
             final RetrieveSubjects command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/SudoRetrievePolicyRevisionStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/SudoRetrievePolicyRevisionStrategy.java
index dc505302dc..8062bc9777 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/SudoRetrievePolicyRevisionStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/SudoRetrievePolicyRevisionStrategy.java
@@ -42,7 +42,7 @@ final class SudoRetrievePolicyRevisionStrategy extends AbstractPolicyQueryComman
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy entity,
             final long nextRevision,
             final SudoRetrievePolicyRevision command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/SudoRetrievePolicyStrategy.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/SudoRetrievePolicyStrategy.java
index e997d99c1f..c65a69f6cf 100644
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/SudoRetrievePolicyStrategy.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/SudoRetrievePolicyStrategy.java
@@ -37,7 +37,7 @@ final class SudoRetrievePolicyStrategy extends AbstractPolicyQueryCommandStrateg
     }
 
     @Override
-    protected Result<PolicyEvent> doApply(final Context<PolicyId> context,
+    protected Result<PolicyEvent<?>> doApply(final Context<PolicyId> context,
             @Nullable final Policy entity,
             final long nextRevision,
             final SudoRetrievePolicy command,
diff --git a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/events/PolicyEventStrategies.java b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/events/PolicyEventStrategies.java
index dad4400ef4..16de6968a3 100755
--- a/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/events/PolicyEventStrategies.java
+++ b/services/policies/persistence/src/main/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/events/PolicyEventStrategies.java
@@ -36,7 +36,7 @@
 /**
  * Holds all {@link org.eclipse.ditto.signals.events.policies.PolicyEvent} strategies.
  */
-public final class PolicyEventStrategies extends AbstractEventStrategies<PolicyEvent, Policy> {
+public final class PolicyEventStrategies extends AbstractEventStrategies<PolicyEvent<?>, Policy> {
 
     private static final PolicyEventStrategies INSTANCE = new PolicyEventStrategies();
 
diff --git a/services/policies/persistence/src/test/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/AbstractPolicyCommandStrategyTest.java b/services/policies/persistence/src/test/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/AbstractPolicyCommandStrategyTest.java
index 3e9ba54ed8..306c2ef8a7 100644
--- a/services/policies/persistence/src/test/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/AbstractPolicyCommandStrategyTest.java
+++ b/services/policies/persistence/src/test/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/AbstractPolicyCommandStrategyTest.java
@@ -64,30 +64,32 @@ protected static CommandStrategy.Context<PolicyId> getDefaultContext() {
         return DefaultContext.getInstance(TestConstants.Policy.POLICY_ID, logger);
     }
 
-    protected static <T extends PolicyEvent<?>> T assertModificationResult(final CommandStrategy underTest,
+    protected static <C extends Command<?>, T extends PolicyEvent<?>> T assertModificationResult(
+            final CommandStrategy<C, Policy, PolicyId, Result<PolicyEvent<?>>> underTest,
             @Nullable final Policy policy,
-            final Command command,
+            final C command,
             final Class<T> expectedEventClass,
-            final CommandResponse expectedCommandResponse) {
+            final CommandResponse<?> expectedCommandResponse) {
 
         return assertModificationResult(underTest, policy, command, expectedEventClass, expectedCommandResponse, false);
     }
 
-    protected static <T extends PolicyEvent<?>, R extends PolicyCommandResponse<R>> void assertModificationResult(
-            final CommandStrategy underTest,
+    protected static <C extends Command<?>, T extends PolicyEvent<?>, R extends PolicyCommandResponse<R>>
+    void assertModificationResult(
+            final CommandStrategy<C, Policy, PolicyId, Result<PolicyEvent<?>>> underTest,
             @Nullable final Policy policy,
-            final Command command,
+            final C command,
             final Class<T> expectedEventClass,
             final Consumer<T> eventSatisfactions,
             final Class<R> expectedResponseClass,
             final Consumer<R> responseSatisfactions) {
 
         final CommandStrategy.Context<PolicyId> context = getDefaultContext();
-        final Result<PolicyEvent> result = applyStrategy(underTest, context, policy, command);
+        final Result<PolicyEvent<?>> result = applyStrategy(underTest, context, policy, command);
 
         final ArgumentCaptor<T> event = ArgumentCaptor.forClass(expectedEventClass);
         final ArgumentCaptor<R> response = ArgumentCaptor.forClass(expectedResponseClass);
-        final ResultVisitor<PolicyEvent> mock = mock(Dummy.class);
+        final ResultVisitor<PolicyEvent<?>> mock = mock(Dummy.class);
         result.accept(mock);
 
         verify(mock).onMutation(any(), event.capture(), response.capture(), anyBoolean(), eq(false));
@@ -95,45 +97,48 @@ protected static <T extends PolicyEvent<?>, R extends PolicyCommandResponse<R>>
         assertThat(response.getValue()).isInstanceOf(expectedResponseClass);
 
         assertThat(event.getValue())
-                .describedAs("Event satisfactions failed for expected event of type '%s'", expectedEventClass.getSimpleName())
+                .describedAs("Event satisfactions failed for expected event of type '%s'",
+                        expectedEventClass.getSimpleName())
                 .satisfies(eventSatisfactions);
         assertThat(response.getValue())
-                .describedAs("Response predicate failed for expected response of type '%s'", expectedResponseClass.getSimpleName())
+                .describedAs("Response predicate failed for expected response of type '%s'",
+                        expectedResponseClass.getSimpleName())
                 .satisfies(responseSatisfactions);
     }
 
-    protected static <T extends PolicyEvent<?>> T assertModificationResult(final CommandStrategy underTest,
+    protected static <C extends Command<?>, T extends PolicyEvent<?>> T assertModificationResult(
+            final CommandStrategy<C, Policy, PolicyId, Result<PolicyEvent<?>>> underTest,
             @Nullable final Policy policy,
-            final Command command,
+            final C command,
             final Class<T> expectedEventClass,
-            final CommandResponse expectedCommandResponse,
+            final CommandResponse<?> expectedCommandResponse,
             final boolean becomeDeleted) {
 
         final CommandStrategy.Context<PolicyId> context = getDefaultContext();
-        final Result<PolicyEvent> result = applyStrategy(underTest, context, policy, command);
+        final Result<PolicyEvent<?>> result = applyStrategy(underTest, context, policy, command);
 
         return assertModificationResult(result, expectedEventClass, expectedCommandResponse, becomeDeleted);
     }
 
-    protected static <C extends Command> void assertErrorResult(
-            final CommandStrategy<C, Policy, PolicyId, Result<PolicyEvent>> underTest,
+    protected static <C extends Command<?>> void assertErrorResult(
+            final CommandStrategy<C, Policy, PolicyId, Result<PolicyEvent<?>>> underTest,
             @Nullable final Policy policy,
             final C command,
             final DittoRuntimeException expectedException) {
 
-        final ResultVisitor<PolicyEvent> mock = mock(Dummy.class);
+        final ResultVisitor<PolicyEvent<?>> mock = mock(Dummy.class);
         applyStrategy(underTest, getDefaultContext(), policy, command).accept(mock);
         verify(mock).onError(eq(expectedException), eq(command));
     }
 
-    private static <T extends PolicyEvent<?>> T assertModificationResult(final Result<PolicyEvent> result,
+    private static <T extends PolicyEvent<?>> T assertModificationResult(final Result<PolicyEvent<?>> result,
             final Class<T> eventClazz,
-            final WithDittoHeaders expectedResponse,
+            final WithDittoHeaders<?> expectedResponse,
             final boolean becomeDeleted) {
 
         final ArgumentCaptor<T> event = ArgumentCaptor.forClass(eventClazz);
 
-        final ResultVisitor<PolicyEvent> mock = mock(Dummy.class);
+        final ResultVisitor<PolicyEvent<?>> mock = mock(Dummy.class);
 
         result.accept(mock);
 
@@ -142,8 +147,8 @@ private static <T extends PolicyEvent<?>> T assertModificationResult(final Resul
         return event.getValue();
     }
 
-    private static <C extends Command> Result<PolicyEvent> applyStrategy(
-            final CommandStrategy<C, Policy, PolicyId, Result<PolicyEvent>> underTest,
+    private static <C extends Command<?>> Result<PolicyEvent<?>> applyStrategy(
+            final CommandStrategy<C, Policy, PolicyId, Result<PolicyEvent<?>>> underTest,
             final CommandStrategy.Context<PolicyId> context,
             @Nullable final Policy policy,
             final C command) {
@@ -151,11 +156,11 @@ private static <C extends Command> Result<PolicyEvent> applyStrategy(
         return underTest.apply(context, policy, NEXT_REVISION, command);
     }
 
-    interface Dummy extends ResultVisitor<PolicyEvent> {}
+    interface Dummy extends ResultVisitor<PolicyEvent<?>> {}
 
     protected static DittoHeaders appendETagToDittoHeaders(final Object object, final DittoHeaders dittoHeaders) {
 
-        return dittoHeaders.toBuilder().eTag(EntityTag.fromEntity(object).get()).build();
+        return dittoHeaders.toBuilder().eTag(EntityTag.fromEntity(object).orElseThrow()).build();
     }
 
 }
diff --git a/services/policies/persistence/src/test/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/PolicyConflictStrategyTest.java b/services/policies/persistence/src/test/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/PolicyConflictStrategyTest.java
index 1f557b8cd6..837d0a6204 100644
--- a/services/policies/persistence/src/test/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/PolicyConflictStrategyTest.java
+++ b/services/policies/persistence/src/test/java/org/eclipse/ditto/services/policies/persistence/actors/strategies/commands/PolicyConflictStrategyTest.java
@@ -60,7 +60,7 @@ public void createConflictResultWithoutPrecondition() {
         final Policy policy = PoliciesModelFactory.newPolicyBuilder(policyId).setRevision(25L).build();
         final CommandStrategy.Context<PolicyId> context = DefaultContext.getInstance(policyId, mockLoggingAdapter());
         final CreatePolicy command = CreatePolicy.of(policy, DittoHeaders.empty());
-        final Result<PolicyEvent> result = underTest.apply(context, policy, 26L, command);
+        final Result<PolicyEvent<?>> result = underTest.apply(context, policy, 26L, command);
         result.accept(new ExpectErrorVisitor(PolicyConflictException.class));
     }
 
@@ -74,7 +74,7 @@ public void createPreconditionFailedResultWithPrecondition() {
         final CreatePolicy command = CreatePolicy.of(policy, DittoHeaders.newBuilder()
                 .ifNoneMatch(EntityTagMatchers.fromStrings("*"))
                 .build());
-        final Result<PolicyEvent> result = underTest.apply(context, policy, 26L, command);
+        final Result<PolicyEvent<?>> result = underTest.apply(context, policy, 26L, command);
         result.accept(new ExpectErrorVisitor(PolicyPreconditionFailedException.class));
     }
 
@@ -84,7 +84,7 @@ private static DittoDiagnosticLoggingAdapter mockLoggingAdapter() {
         return mock;
     }
 
-    private static final class ExpectErrorVisitor implements ResultVisitor<PolicyEvent> {
+    private static final class ExpectErrorVisitor implements ResultVisitor<PolicyEvent<?>> {
 
         private final Class<? extends DittoRuntimeException> clazz;
 
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/ThingPersistenceActor.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/ThingPersistenceActor.java
index a4e65b11e5..1912569ba5 100755
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/ThingPersistenceActor.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/ThingPersistenceActor.java
@@ -47,7 +47,7 @@
  * PersistentActor which "knows" the state of a single {@link Thing}.
  */
 public final class ThingPersistenceActor
-        extends AbstractShardedPersistenceActor<Command, Thing, ThingId, ThingId, ThingEvent> {
+        extends AbstractShardedPersistenceActor<Command<?>, Thing, ThingId, ThingId, ThingEvent<?>> {
 
     /**
      * The prefix of the persistenceId for Things.
@@ -64,7 +64,7 @@ public final class ThingPersistenceActor
      */
     static final String SNAPSHOT_PLUGIN_ID = "akka-contrib-mongodb-persistence-things-snapshots";
 
-    private static AckExtractor<ThingEvent<?>> ACK_EXTRACTOR =
+    private static final AckExtractor<ThingEvent<?>> ACK_EXTRACTOR =
             AckExtractor.of(ThingEvent::getEntityId, ThingEvent::getDittoHeaders);
 
     private final ThingConfig thingConfig;
@@ -123,7 +123,7 @@ public String snapshotPluginId() {
     }
 
     @Override
-    protected Class<ThingEvent> getEventClass() {
+    protected Class<?> getEventClass() {
         return ThingEvent.class;
     }
 
@@ -138,12 +138,12 @@ protected ThingCommandStrategies getCreatedStrategy() {
     }
 
     @Override
-    protected CommandStrategy<CreateThing, Thing, ThingId, Result<ThingEvent>> getDeletedStrategy() {
+    protected CommandStrategy<CreateThing, Thing, ThingId, Result<ThingEvent<?>>> getDeletedStrategy() {
         return ThingCommandStrategies.getCreateThingStrategy();
     }
 
     @Override
-    protected EventStrategy<ThingEvent, Thing> getEventStrategy() {
+    protected EventStrategy<ThingEvent<?>, Thing> getEventStrategy() {
         return ThingEventStrategies.getInstance();
     }
 
@@ -163,7 +163,7 @@ protected boolean entityExistsAsDeleted() {
     }
 
     @Override
-    protected DittoRuntimeExceptionBuilder newNotAccessibleExceptionBuilder() {
+    protected DittoRuntimeExceptionBuilder<?> newNotAccessibleExceptionBuilder() {
         return ThingNotAccessibleException.newBuilder(entityId);
     }
 
@@ -177,7 +177,7 @@ protected void recoveryCompleted(final RecoveryCompleted event) {
     }
 
     @Override
-    protected void publishEvent(final ThingEvent event) {
+    protected void publishEvent(final ThingEvent<?> event) {
         distributedPub.publishWithAcks(event, ACK_EXTRACTOR, getSender());
     }
 
@@ -188,7 +188,7 @@ protected JsonSchemaVersion getEntitySchemaVersion(final Thing entity) {
 
     private static Thing enhanceThingWithLifecycle(final Thing thing) {
         final ThingBuilder.FromCopy thingBuilder = ThingsModelFactory.newThingBuilder(thing);
-        if (!thing.getLifecycle().isPresent()) {
+        if (thing.getLifecycle().isEmpty()) {
             thingBuilder.setLifecycle(ThingLifecycle.ACTIVE);
         }
 
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/AbstractThingCommandStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/AbstractThingCommandStrategy.java
index 010d36fef4..3b0237609d 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/AbstractThingCommandStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/AbstractThingCommandStrategy.java
@@ -36,7 +36,7 @@
  */
 @Immutable
 abstract class AbstractThingCommandStrategy<C extends Command<C>>
-        extends AbstractConditionHeaderCheckingCommandStrategy<C, Thing, ThingId, ThingEvent> {
+        extends AbstractConditionHeaderCheckingCommandStrategy<C, Thing, ThingId, ThingEvent<?>> {
 
     private static final ConditionalHeadersValidator VALIDATOR =
             ThingsConditionalHeadersValidatorProvider.getInstance();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/CreateThingStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/CreateThingStrategy.java
index 61f40afb2e..471bea6897 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/CreateThingStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/CreateThingStrategy.java
@@ -82,7 +82,7 @@ public boolean isDefined(final Context<ThingId> context, @Nullable final Thing t
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final CreateThing command,
@@ -101,7 +101,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
         }
 
         // before persisting, check if the Thing is valid and reject if not:
-        final Result validateThingError =
+        final Result<ThingEvent<?>> validateThingError =
                 validateThing(context, command.getImplementedSchemaVersion(), newThing, command);
         if (validateThingError != null) {
             return validateThingError;
@@ -188,8 +188,8 @@ private Thing enhanceNewThingWithFallbackAcl(final Thing newThing, final Authori
     }
 
     @Nullable
-    private Result validateThing(final Context<ThingId> context, final JsonSchemaVersion version, final Thing thing,
-            final CreateThing command) {
+    private Result<ThingEvent<?>> validateThing(final Context<ThingId> context, final JsonSchemaVersion version,
+            final Thing thing, final CreateThing command) {
         final DittoHeaders headers = command.getDittoHeaders();
         final Optional<AccessControlList> accessControlList = thing.getAccessControlList();
         if (JsonSchemaVersion.V_1.equals(version)) {
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteAclEntryStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteAclEntryStrategy.java
index 5d95d3e8c5..45d6591758 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteAclEntryStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteAclEntryStrategy.java
@@ -48,7 +48,7 @@ final class DeleteAclEntryStrategy extends AbstractThingCommandStrategy<DeleteAc
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final DeleteAclEntry command,
@@ -71,7 +71,7 @@ private Optional<AccessControlList> extractAcl(@Nullable final Thing thing, fina
                 .filter(acl -> acl.contains(authSubject));
     }
 
-    private Result<ThingEvent> getDeleteAclEntryResult(final AccessControlList acl, final Context<ThingId> context,
+    private Result<ThingEvent<?>> getDeleteAclEntryResult(final AccessControlList acl, final Context<ThingId> context,
             final long nextRevision, final DeleteAclEntry command, @Nullable final Thing thing,
             @Nullable final Metadata metadata) {
 
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteAttributeStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteAttributeStrategy.java
index 0d024e840a..cf43726a5b 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteAttributeStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteAttributeStrategy.java
@@ -46,7 +46,7 @@ final class DeleteAttributeStrategy extends AbstractThingCommandStrategy<DeleteA
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final DeleteAttribute command,
@@ -63,7 +63,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
                                 command.getDittoHeaders()), command));
     }
 
-    private Result<ThingEvent> getDeleteAttributeResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getDeleteAttributeResult(final Context<ThingId> context, final long nextRevision,
             final DeleteAttribute command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
         final ThingId thingId = context.getState();
         final JsonPointer attrPointer = command.getAttributePointer();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteAttributesStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteAttributesStrategy.java
index bb9dc76931..ba9e7ea304 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteAttributesStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteAttributesStrategy.java
@@ -46,7 +46,7 @@ final class DeleteAttributesStrategy
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final DeleteAttributes command,
@@ -62,7 +62,7 @@ private Optional<Attributes> extractAttributes(final @Nullable Thing thing) {
         return getEntityOrThrow(thing).getAttributes();
     }
 
-    private Result<ThingEvent> getDeleteAttributesResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getDeleteAttributesResult(final Context<ThingId> context, final long nextRevision,
             final DeleteAttributes command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
         final ThingId thingId = context.getState();
         final DittoHeaders dittoHeaders = command.getDittoHeaders();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureDefinitionStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureDefinitionStrategy.java
index a8d68a3a01..09b6299c11 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureDefinitionStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureDefinitionStrategy.java
@@ -45,7 +45,7 @@ final class DeleteFeatureDefinitionStrategy extends AbstractThingCommandStrategy
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final DeleteFeatureDefinition command,
@@ -60,7 +60,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
                                 command.getDittoHeaders()), command));
     }
 
-    private Result<ThingEvent> getDeleteFeatureDefinitionResult(final Feature feature, final Context<ThingId> context,
+    private Result<ThingEvent<?>> getDeleteFeatureDefinitionResult(final Feature feature, final Context<ThingId> context,
             final long nextRevision, final DeleteFeatureDefinition command, @Nullable final Thing thing,
             @Nullable final Metadata metadata) {
         final DittoHeaders dittoHeaders = command.getDittoHeaders();
@@ -70,12 +70,12 @@ private Result<ThingEvent> getDeleteFeatureDefinitionResult(final Feature featur
 
         return feature.getDefinition()
                 .map(featureDefinition -> {
-                    final ThingEvent event =
+                    final ThingEvent<?> event =
                             FeatureDefinitionDeleted.of(thingId, featureId, nextRevision, getEventTimestamp(),
                                     dittoHeaders, metadata);
-                    final WithDittoHeaders response = appendETagHeaderIfProvided(command,
+                    final WithDittoHeaders<?> response = appendETagHeaderIfProvided(command,
                             DeleteFeatureDefinitionResponse.of(thingId, featureId, dittoHeaders), thing);
-                    return ResultFactory.newMutationResult(command, event, response);
+                    return ResultFactory.<ThingEvent<?>>newMutationResult(command, event, response);
                 })
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         ExceptionFactory.featureDefinitionNotFound(thingId, featureId, dittoHeaders), command));
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureDesiredPropertiesStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureDesiredPropertiesStrategy.java
index d4fb80a492..c8849ab9a3 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureDesiredPropertiesStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureDesiredPropertiesStrategy.java
@@ -46,7 +46,7 @@ final class DeleteFeatureDesiredPropertiesStrategy
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final DeleteFeatureDesiredProperties command,
@@ -67,7 +67,7 @@ private Optional<Feature> extractFeature(final DeleteFeatureDesiredProperties co
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getDeleteFeatureDesiredPropertiesResult(final Feature feature,
+    private Result<ThingEvent<?>> getDeleteFeatureDesiredPropertiesResult(final Feature feature,
             final Context<ThingId> context,
             final long nextRevision,
             final DeleteFeatureDesiredProperties command,
@@ -80,12 +80,12 @@ private Result<ThingEvent> getDeleteFeatureDesiredPropertiesResult(final Feature
 
         return feature.getDesiredProperties()
                 .map(desiredProperties -> {
-                    final ThingEvent event =
+                    final ThingEvent<?> event =
                             FeatureDesiredPropertiesDeleted.of(thingId, featureId, nextRevision, getEventTimestamp(),
                                     dittoHeaders, metadata);
-                    final WithDittoHeaders response = appendETagHeaderIfProvided(command,
+                    final WithDittoHeaders<?> response = appendETagHeaderIfProvided(command,
                             DeleteFeatureDesiredPropertiesResponse.of(thingId, featureId, dittoHeaders), thing);
-                    return ResultFactory.newMutationResult(command, event, response);
+                    return ResultFactory.<ThingEvent<?>>newMutationResult(command, event, response);
                 })
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         ExceptionFactory.featureDesiredPropertiesNotFound(thingId, featureId, dittoHeaders), command));
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureDesiredPropertyStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureDesiredPropertyStrategy.java
index 0b2c05ee99..fb10cd56bf 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureDesiredPropertyStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureDesiredPropertyStrategy.java
@@ -46,7 +46,7 @@ final class DeleteFeatureDesiredPropertyStrategy extends AbstractThingCommandStr
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final DeleteFeatureDesiredProperty command,
@@ -65,7 +65,7 @@ private Optional<Feature> extractFeature(final DeleteFeatureDesiredProperty comm
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getDeleteFeatureDesiredPropertyResult(final Feature feature,
+    private Result<ThingEvent<?>> getDeleteFeatureDesiredPropertyResult(final Feature feature,
             final Context<ThingId> context,
             final long nextRevision,
             final DeleteFeatureDesiredProperty command,
@@ -79,11 +79,11 @@ private Result<ThingEvent> getDeleteFeatureDesiredPropertyResult(final Feature f
 
         return feature.getDesiredProperties()
                 .flatMap(desiredProperties -> desiredProperties.getValue(desiredPropertyPointer))
-                .map(FeatureDesiredProperty -> {
-                    final ThingEvent event =
+                .<Result<ThingEvent<?>>>map(FeatureDesiredProperty -> {
+                    final ThingEvent<?> event =
                             FeatureDesiredPropertyDeleted.of(thingId, featureId, desiredPropertyPointer, nextRevision,
                                     getEventTimestamp(), dittoHeaders, metadata);
-                    final WithDittoHeaders response = appendETagHeaderIfProvided(command,
+                    final WithDittoHeaders<?> response = appendETagHeaderIfProvided(command,
                             DeleteFeatureDesiredPropertyResponse.of(thingId, featureId, desiredPropertyPointer,
                                     dittoHeaders), thing);
                     return ResultFactory.newMutationResult(command, event, response);
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeaturePropertiesStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeaturePropertiesStrategy.java
index 614c61ae59..b3b0d4d325 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeaturePropertiesStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeaturePropertiesStrategy.java
@@ -45,7 +45,7 @@ final class DeleteFeaturePropertiesStrategy extends AbstractThingCommandStrategy
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final DeleteFeatureProperties command,
@@ -66,7 +66,7 @@ private Optional<Feature> extractFeature(final DeleteFeatureProperties command,
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getDeleteFeaturePropertiesResult(final Feature feature, final Context<ThingId> context,
+    private Result<ThingEvent<?>> getDeleteFeaturePropertiesResult(final Feature feature, final Context<ThingId> context,
             final long nextRevision, final DeleteFeatureProperties command, @Nullable final Thing thing,
             @Nullable final Metadata metadata) {
         final DittoHeaders dittoHeaders = command.getDittoHeaders();
@@ -76,12 +76,12 @@ private Result<ThingEvent> getDeleteFeaturePropertiesResult(final Feature featur
 
         return feature.getProperties()
                 .map(featureProperties -> {
-                    final ThingEvent event =
+                    final ThingEvent<?> event =
                             FeaturePropertiesDeleted.of(thingId, featureId, nextRevision, getEventTimestamp(),
                                     dittoHeaders, metadata);
-                    final WithDittoHeaders response = appendETagHeaderIfProvided(command,
+                    final WithDittoHeaders<?> response = appendETagHeaderIfProvided(command,
                             DeleteFeaturePropertiesResponse.of(thingId, featureId, dittoHeaders), thing);
-                    return ResultFactory.newMutationResult(command, event, response);
+                    return ResultFactory.<ThingEvent<?>>newMutationResult(command, event, response);
                 })
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         ExceptionFactory.featurePropertiesNotFound(thingId, featureId, dittoHeaders), command));
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeaturePropertyStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeaturePropertyStrategy.java
index e6dcd68802..e1bd1e0113 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeaturePropertyStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeaturePropertyStrategy.java
@@ -46,7 +46,7 @@ final class DeleteFeaturePropertyStrategy extends AbstractThingCommandStrategy<D
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final DeleteFeatureProperty command,
@@ -65,7 +65,7 @@ private Optional<Feature> extractFeature(final DeleteFeatureProperty command, fi
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getDeleteFeaturePropertyResult(final Feature feature, final Context<ThingId> context,
+    private Result<ThingEvent<?>> getDeleteFeaturePropertyResult(final Feature feature, final Context<ThingId> context,
             final long nextRevision, final DeleteFeatureProperty command, @Nullable final Thing thing,
             @Nullable final Metadata metadata) {
 
@@ -77,12 +77,12 @@ private Result<ThingEvent> getDeleteFeaturePropertyResult(final Feature feature,
         return feature.getProperties()
                 .flatMap(featureProperties -> featureProperties.getValue(propertyPointer))
                 .map(featureProperty -> {
-                    final ThingEvent event =
+                    final ThingEvent<?> event =
                             FeaturePropertyDeleted.of(thingId, featureId, propertyPointer, nextRevision,
                                     getEventTimestamp(), dittoHeaders, metadata);
-                    final WithDittoHeaders response = appendETagHeaderIfProvided(command,
+                    final WithDittoHeaders<?> response = appendETagHeaderIfProvided(command,
                             DeleteFeaturePropertyResponse.of(thingId, featureId, propertyPointer, dittoHeaders), thing);
-                    return ResultFactory.newMutationResult(command, event, response);
+                    return ResultFactory.<ThingEvent<?>>newMutationResult(command, event, response);
                 })
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         ExceptionFactory.featurePropertyNotFound(thingId, featureId, propertyPointer, dittoHeaders),
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureStrategy.java
index 8115d97e37..4ca7831913 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeatureStrategy.java
@@ -45,7 +45,7 @@ final class DeleteFeatureStrategy extends AbstractThingCommandStrategy<DeleteFea
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final DeleteFeature command,
@@ -67,7 +67,7 @@ private Optional<Feature> extractFeature(final DeleteFeature command, @Nullable
                 .flatMap(features -> features.getFeature(featureId));
     }
 
-    private Result<ThingEvent> getDeleteFeatureResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getDeleteFeatureResult(final Context<ThingId> context, final long nextRevision,
             final DeleteFeature command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final ThingId thingId = context.getState();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeaturesStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeaturesStrategy.java
index 7c32262383..6460dc94c0 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeaturesStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteFeaturesStrategy.java
@@ -45,7 +45,7 @@ final class DeleteFeaturesStrategy extends AbstractThingCommandStrategy<DeleteFe
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final DeleteFeatures command,
@@ -55,7 +55,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
 
         return extractFeatures(thing)
                 .map(features ->
-                        ResultFactory.newMutationResult(command,
+                        ResultFactory.<ThingEvent<?>>newMutationResult(command,
                                 getEventToPersist(context, nextRevision, dittoHeaders, metadata),
                                 getResponse(context, command, thing))
                 )
@@ -68,13 +68,13 @@ private Optional<Features> extractFeatures(final @Nullable Thing thing) {
         return getEntityOrThrow(thing).getFeatures();
     }
 
-    private static ThingEvent getEventToPersist(final Context<ThingId> context, final long nextRevision,
+    private static ThingEvent<?> getEventToPersist(final Context<ThingId> context, final long nextRevision,
             final DittoHeaders dittoHeaders, @Nullable final Metadata metadata) {
 
         return FeaturesDeleted.of(context.getState(), nextRevision, getEventTimestamp(), dittoHeaders, metadata);
     }
 
-    private WithDittoHeaders getResponse(final Context<ThingId> context, final DeleteFeatures command,
+    private WithDittoHeaders<?> getResponse(final Context<ThingId> context, final DeleteFeatures command,
             @Nullable final Thing thing) {
         return appendETagHeaderIfProvided(command,
                 DeleteFeaturesResponse.of(context.getState(), command.getDittoHeaders()), thing);
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteThingDefinitionStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteThingDefinitionStrategy.java
index dccf93725f..5a7ecd01e7 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteThingDefinitionStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteThingDefinitionStrategy.java
@@ -47,7 +47,7 @@ final class DeleteThingDefinitionStrategy
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final DeleteThingDefinition command,
@@ -65,7 +65,7 @@ private Optional<ThingDefinition> extractDefinition(final @Nullable Thing thing)
         return getEntityOrThrow(thing).getDefinition();
     }
 
-    private Result<ThingEvent> getDeleteDefinitionResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getDeleteDefinitionResult(final Context<ThingId> context, final long nextRevision,
             final DeleteThingDefinition command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final ThingId thingId = context.getState();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteThingStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteThingStrategy.java
index fad474ab66..1d1f4853a1 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteThingStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/DeleteThingStrategy.java
@@ -44,7 +44,7 @@ final class DeleteThingStrategy extends AbstractThingCommandStrategy<DeleteThing
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final DeleteThing command,
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAclEntryStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAclEntryStrategy.java
index b067e5238d..6b4d77340a 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAclEntryStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAclEntryStrategy.java
@@ -50,7 +50,7 @@ final class ModifyAclEntryStrategy extends AbstractThingCommandStrategy<ModifyAc
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyAclEntry command,
@@ -74,7 +74,7 @@ private static Validator getAclValidator(final AccessControlList acl) {
         return AclValidator.newInstance(acl, Thing.MIN_REQUIRED_PERMISSIONS);
     }
 
-    private Result<ThingEvent> getModifyOrCreateResult(final AccessControlList acl, final Context<ThingId> context,
+    private Result<ThingEvent<?>> getModifyOrCreateResult(final AccessControlList acl, final Context<ThingId> context,
             final long nextRevision, final ModifyAclEntry command, @Nullable final Thing thing,
             @Nullable final Metadata metadata) {
 
@@ -85,7 +85,7 @@ private Result<ThingEvent> getModifyOrCreateResult(final AccessControlList acl,
         return getCreateResult(context, nextRevision, command, thing, metadata);
     }
 
-    private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getModifyResult(final Context<ThingId> context, final long nextRevision,
             final ModifyAclEntry command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
         final ThingId thingId = context.getState();
         final AclEntry aclEntry = command.getAclEntry();
@@ -99,7 +99,7 @@ private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final
         return ResultFactory.newMutationResult(command, event, response);
     }
 
-    private Result<ThingEvent> getCreateResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getCreateResult(final Context<ThingId> context, final long nextRevision,
             final ModifyAclEntry command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
         final ThingId thingId = context.getState();
         final AclEntry aclEntry = command.getAclEntry();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAclStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAclStrategy.java
index 04a63c1b75..874ebda7fb 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAclStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAclStrategy.java
@@ -47,7 +47,7 @@ final class ModifyAclStrategy extends AbstractThingCommandStrategy<ModifyAcl> {
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyAcl command,
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAttributeStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAttributeStrategy.java
index 3dd1f3c5a8..a18f6dd0eb 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAttributeStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAttributeStrategy.java
@@ -49,7 +49,7 @@ final class ModifyAttributeStrategy extends AbstractThingCommandStrategy<ModifyA
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyAttribute command,
@@ -81,7 +81,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
                 .orElseGet(() -> getCreateResult(context, nextRevision, command, thing, metadata));
     }
 
-    private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getModifyResult(final Context<ThingId> context, final long nextRevision,
             final ModifyAttribute command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final ThingId thingId = context.getState();
@@ -97,7 +97,7 @@ private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final
         return ResultFactory.newMutationResult(command, event, response);
     }
 
-    private Result<ThingEvent> getCreateResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getCreateResult(final Context<ThingId> context, final long nextRevision,
             final ModifyAttribute command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final ThingId thingId = context.getState();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAttributesStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAttributesStrategy.java
index f48eff1d95..96f5d64f10 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAttributesStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyAttributesStrategy.java
@@ -48,7 +48,7 @@ final class ModifyAttributesStrategy extends AbstractThingCommandStrategy<Modify
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyAttributes command,
@@ -79,7 +79,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
                 .orElseGet(() -> getCreateResult(context, nextRevision, command, thing, metadata));
     }
 
-    private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getModifyResult(final Context<ThingId> context, final long nextRevision,
             final ModifyAttributes command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
         final ThingId thingId = context.getState();
         final DittoHeaders dittoHeaders = command.getDittoHeaders();
@@ -93,7 +93,7 @@ private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final
         return ResultFactory.newMutationResult(command, event, response);
     }
 
-    private Result<ThingEvent> getCreateResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getCreateResult(final Context<ThingId> context, final long nextRevision,
             final ModifyAttributes command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
         final ThingId thingId = context.getState();
         final Attributes attributes = command.getAttributes();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureDefinitionStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureDefinitionStrategy.java
index 11ec6be6ef..9e9d602a46 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureDefinitionStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureDefinitionStrategy.java
@@ -46,7 +46,7 @@ final class ModifyFeatureDefinitionStrategy extends AbstractThingCommandStrategy
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyFeatureDefinition command,
@@ -66,7 +66,7 @@ private Optional<Feature> extractFeature(final ModifyFeatureDefinition command,
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getModifyOrCreateResult(final Feature feature, final Context<ThingId> context,
+    private Result<ThingEvent<?>> getModifyOrCreateResult(final Feature feature, final Context<ThingId> context,
             final long nextRevision, final ModifyFeatureDefinition command, @Nullable final Thing thing,
             @Nullable final Metadata metadata) {
 
@@ -75,7 +75,7 @@ private Result<ThingEvent> getModifyOrCreateResult(final Feature feature, final
                 .orElseGet(() -> getCreateResult(context, nextRevision, command, thing, metadata));
     }
 
-    private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getModifyResult(final Context<ThingId> context, final long nextRevision,
             final ModifyFeatureDefinition command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final ThingId thingId = context.getState();
@@ -91,7 +91,7 @@ private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final
         return ResultFactory.newMutationResult(command, event, response);
     }
 
-    private Result<ThingEvent> getCreateResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getCreateResult(final Context<ThingId> context, final long nextRevision,
             final ModifyFeatureDefinition command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final ThingId thingId = context.getState();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureDesiredPropertiesStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureDesiredPropertiesStrategy.java
index 533ec94142..148a446131 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureDesiredPropertiesStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureDesiredPropertiesStrategy.java
@@ -50,7 +50,7 @@ final class ModifyFeatureDesiredPropertiesStrategy
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyFeatureDesiredProperties command,
@@ -94,7 +94,7 @@ private Optional<Feature> extractFeature(final ModifyFeatureDesiredProperties co
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getModifyOrCreateResult(final Feature feature,
+    private Result<ThingEvent<?>> getModifyOrCreateResult(final Feature feature,
             final Context<ThingId> context,
             final long nextRevision,
             final ModifyFeatureDesiredProperties command,
@@ -106,7 +106,7 @@ private Result<ThingEvent> getModifyOrCreateResult(final Feature feature,
                 .orElseGet(() -> getCreateResult(context, nextRevision, command, thing, metadata));
     }
 
-    private Result<ThingEvent> getModifyResult(final Context<ThingId> context,
+    private Result<ThingEvent<?>> getModifyResult(final Context<ThingId> context,
             final long nextRevision,
             final ModifyFeatureDesiredProperties command,
             @Nullable final Thing thing,
@@ -125,7 +125,7 @@ private Result<ThingEvent> getModifyResult(final Context<ThingId> context,
         return ResultFactory.newMutationResult(command, event, response);
     }
 
-    private Result<ThingEvent> getCreateResult(final Context<ThingId> context,
+    private Result<ThingEvent<?>> getCreateResult(final Context<ThingId> context,
             final long nextRevision,
             final ModifyFeatureDesiredProperties command,
             @Nullable final Thing thing,
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureDesiredPropertyStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureDesiredPropertyStrategy.java
index 273937e28b..58588e835e 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureDesiredPropertyStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureDesiredPropertyStrategy.java
@@ -50,7 +50,7 @@ final class ModifyFeatureDesiredPropertyStrategy extends AbstractThingCommandStr
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyFeatureDesiredProperty command,
@@ -93,7 +93,7 @@ private Optional<Feature> extractFeature(final ModifyFeatureDesiredProperty comm
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getModifyOrCreateResult(final Feature feature,
+    private Result<ThingEvent<?>> getModifyOrCreateResult(final Feature feature,
             final Context<ThingId> context,
             final long nextRevision,
             final ModifyFeatureDesiredProperty command,
@@ -106,7 +106,7 @@ private Result<ThingEvent> getModifyOrCreateResult(final Feature feature,
                 .orElseGet(() -> getCreateResult(context, nextRevision, command, thing, metadata));
     }
 
-    private Result<ThingEvent> getModifyResult(final Context<ThingId> context,
+    private Result<ThingEvent<?>> getModifyResult(final Context<ThingId> context,
             final long nextRevision,
             final ModifyFeatureDesiredProperty command,
             @Nullable final Thing thing,
@@ -127,7 +127,7 @@ private Result<ThingEvent> getModifyResult(final Context<ThingId> context,
         return ResultFactory.newMutationResult(command, event, response);
     }
 
-    private Result<ThingEvent> getCreateResult(final Context<ThingId> context,
+    private Result<ThingEvent<?>> getCreateResult(final Context<ThingId> context,
             final long nextRevision,
             final ModifyFeatureDesiredProperty command,
             @Nullable final Thing thing,
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeaturePropertiesStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeaturePropertiesStrategy.java
index 6fa0b07b31..cce2d893cf 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeaturePropertiesStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeaturePropertiesStrategy.java
@@ -49,7 +49,7 @@ final class ModifyFeaturePropertiesStrategy extends AbstractThingCommandStrategy
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyFeatureProperties command,
@@ -90,7 +90,7 @@ private Optional<Feature> extractFeature(final ModifyFeatureProperties command,
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getModifyOrCreateResult(final Feature feature, final Context<ThingId> context,
+    private Result<ThingEvent<?>> getModifyOrCreateResult(final Feature feature, final Context<ThingId> context,
             final long nextRevision, final ModifyFeatureProperties command, @Nullable final Thing thing,
             @Nullable final Metadata metadata) {
 
@@ -99,7 +99,7 @@ private Result<ThingEvent> getModifyOrCreateResult(final Feature feature, final
                 .orElseGet(() -> getCreateResult(context, nextRevision, command, thing, metadata));
     }
 
-    private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getModifyResult(final Context<ThingId> context, final long nextRevision,
             final ModifyFeatureProperties command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final ThingId thingId = context.getState();
@@ -115,7 +115,7 @@ private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final
         return ResultFactory.newMutationResult(command, event, response);
     }
 
-    private Result<ThingEvent> getCreateResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getCreateResult(final Context<ThingId> context, final long nextRevision,
             final ModifyFeatureProperties command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final ThingId thingId = context.getState();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeaturePropertyStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeaturePropertyStrategy.java
index b280f8d17d..246e7faf82 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeaturePropertyStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeaturePropertyStrategy.java
@@ -50,7 +50,7 @@ final class ModifyFeaturePropertyStrategy extends AbstractThingCommandStrategy<M
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyFeatureProperty command,
@@ -88,7 +88,7 @@ private Optional<Feature> extractFeature(final ModifyFeatureProperty command, @N
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getModifyOrCreateResult(final Feature feature, final Context<ThingId> context,
+    private Result<ThingEvent<?>> getModifyOrCreateResult(final Feature feature, final Context<ThingId> context,
             final long nextRevision, final ModifyFeatureProperty command, @Nullable final Thing thing,
             @Nullable final Metadata metadata) {
 
@@ -98,7 +98,7 @@ private Result<ThingEvent> getModifyOrCreateResult(final Feature feature, final
                 .orElseGet(() -> getCreateResult(context, nextRevision, command, thing, metadata));
     }
 
-    private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getModifyResult(final Context<ThingId> context, final long nextRevision,
             final ModifyFeatureProperty command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final String featureId = command.getFeatureId();
@@ -115,7 +115,7 @@ private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final
         return ResultFactory.newMutationResult(command, event, response);
     }
 
-    private Result<ThingEvent> getCreateResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getCreateResult(final Context<ThingId> context, final long nextRevision,
             final ModifyFeatureProperty command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final String featureId = command.getFeatureId();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureStrategy.java
index 8748e9b5f8..95274c6812 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeatureStrategy.java
@@ -48,7 +48,7 @@ final class ModifyFeatureStrategy extends AbstractThingCommandStrategy<ModifyFea
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyFeature command,
@@ -85,7 +85,7 @@ private Optional<Feature> extractFeature(final ModifyFeature command, @Nullable
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getModifyResult(final Context<ThingId> context, final long nextRevision,
             final ModifyFeature command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final DittoHeaders dittoHeaders = command.getDittoHeaders();
@@ -100,7 +100,7 @@ private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final
         return ResultFactory.newMutationResult(command, event, response);
     }
 
-    private Result<ThingEvent> getCreateResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getCreateResult(final Context<ThingId> context, final long nextRevision,
             final ModifyFeature command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final DittoHeaders dittoHeaders = command.getDittoHeaders();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeaturesStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeaturesStrategy.java
index fa10c801ea..8eddf673bb 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeaturesStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyFeaturesStrategy.java
@@ -48,7 +48,7 @@ final class ModifyFeaturesStrategy extends AbstractThingCommandStrategy<ModifyFe
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyFeatures command,
@@ -77,7 +77,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
                 .orElseGet(() -> getCreateResult(context, nextRevision, command, thing, metadata));
     }
 
-    private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getModifyResult(final Context<ThingId> context, final long nextRevision,
             final ModifyFeatures command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final DittoHeaders dittoHeaders = command.getDittoHeaders();
@@ -91,7 +91,7 @@ private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final
         return ResultFactory.newMutationResult(command, event, response);
     }
 
-    private Result<ThingEvent> getCreateResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getCreateResult(final Context<ThingId> context, final long nextRevision,
             final ModifyFeatures command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final Features features = command.getFeatures();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyPolicyIdStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyPolicyIdStrategy.java
index 5f3ac13d0d..49e24f3b1e 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyPolicyIdStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyPolicyIdStrategy.java
@@ -46,7 +46,7 @@ final class ModifyPolicyIdStrategy extends AbstractThingCommandStrategy<ModifyPo
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyPolicyId command,
@@ -61,7 +61,7 @@ private Optional<PolicyId> extractPolicyId(final @Nullable Thing thing) {
         return getEntityOrThrow(thing).getPolicyEntityId();
     }
 
-    private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getModifyResult(final Context<ThingId> context, final long nextRevision,
             final ModifyPolicyId command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final ThingId thingId = context.getState();
@@ -76,7 +76,7 @@ private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final
         return ResultFactory.newMutationResult(command, event, response);
     }
 
-    private Result<ThingEvent> getCreateResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getCreateResult(final Context<ThingId> context, final long nextRevision,
             final ModifyPolicyId command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final ThingId thingId = context.getState();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyThingDefinitionStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyThingDefinitionStrategy.java
index 741a2f2451..dda15ec824 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyThingDefinitionStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyThingDefinitionStrategy.java
@@ -46,7 +46,7 @@ final class ModifyThingDefinitionStrategy extends AbstractThingCommandStrategy<M
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyThingDefinition command,
@@ -61,7 +61,7 @@ private Optional<ThingDefinition> extractDefinition(final @Nullable Thing thing)
         return getEntityOrThrow(thing).getDefinition();
     }
 
-    private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getModifyResult(final Context<ThingId> context, final long nextRevision,
             final ModifyThingDefinition command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final ThingId thingId = context.getState();
@@ -76,7 +76,7 @@ private Result<ThingEvent> getModifyResult(final Context<ThingId> context, final
         return ResultFactory.newMutationResult(command, event, response);
     }
 
-    private Result<ThingEvent> getCreateResult(final Context<ThingId> context, final long nextRevision,
+    private Result<ThingEvent<?>> getCreateResult(final Context<ThingId> context, final long nextRevision,
             final ModifyThingDefinition command, @Nullable final Thing thing, @Nullable final Metadata metadata) {
 
         final ThingId thingId = context.getState();
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyThingStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyThingStrategy.java
index 1f66e86879..58e77648a1 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyThingStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ModifyThingStrategy.java
@@ -55,7 +55,7 @@ final class ModifyThingStrategy extends AbstractThingCommandStrategy<ModifyThing
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final ModifyThing command,
@@ -78,7 +78,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
         return handleModifyExistingWithV2Command(context, nonNullThing, eventTs, nextRevision, command, metadata);
     }
 
-    private Result<ThingEvent> handleModifyExistingWithV1Command(final Context<ThingId> context, final Thing thing,
+    private Result<ThingEvent<?>> handleModifyExistingWithV1Command(final Context<ThingId> context, final Thing thing,
             final Instant eventTs, final long nextRevision, final ModifyThing command,
             @Nullable final Metadata metadata) {
 
@@ -89,7 +89,7 @@ private Result<ThingEvent> handleModifyExistingWithV1Command(final Context<Thing
         }
     }
 
-    private Result<ThingEvent> handleModifyExistingV1WithV1Command(final Context<ThingId> context,
+    private Result<ThingEvent<?>> handleModifyExistingV1WithV1Command(final Context<ThingId> context,
             final Thing thing, final Instant eventTs, final long nextRevision, final ModifyThing command,
             @Nullable final Metadata metadata) {
 
@@ -111,9 +111,9 @@ private Result<ThingEvent> handleModifyExistingV1WithV1Command(final Context<Thi
                 final Thing newThingWithoutAcl = command.getThing().toBuilder().removeAllPermissions().build();
                 final Thing mergedThing = mergeThingModifications(newThingWithoutAcl, thing, eventTs, nextRevision);
 
-                final ThingEvent thingModified =
+                final ThingEvent<?>thingModified =
                         ThingModified.of(mergedThing, nextRevision, eventTs, dittoHeaders, metadata);
-                final WithDittoHeaders response =
+                final WithDittoHeaders<?> response =
                         appendETagHeaderIfProvided(command, ModifyThingResponse.modified(thingId, dittoHeaders),
                                 mergedThing);
                 return ResultFactory.newMutationResult(command, thingModified, response);
@@ -126,9 +126,9 @@ private Result<ThingEvent> handleModifyExistingV1WithV1Command(final Context<Thi
                         .setModified(eventTs)
                         .setRevision(nextRevision)
                         .build();
-                final ThingEvent thingModified =
+                final ThingEvent<?>thingModified =
                         ThingModified.of(modifiedThing, nextRevision, eventTs, dittoHeaders, metadata);
-                final WithDittoHeaders response =
+                final WithDittoHeaders<?> response =
                         appendETagHeaderIfProvided(command, ModifyThingResponse.modified(thingId, dittoHeaders),
                                 modifiedThing);
                 return ResultFactory.newMutationResult(command, thingModified, response);
@@ -136,7 +136,7 @@ private Result<ThingEvent> handleModifyExistingV1WithV1Command(final Context<Thi
         }
     }
 
-    private Result<ThingEvent> handleModifyExistingV2WithV1Command(final Context<ThingId> context,
+    private Result<ThingEvent<?>> handleModifyExistingV2WithV1Command(final Context<ThingId> context,
             final Thing thing, final Instant eventTs, final long nextRevision,
             final ModifyThing command, @Nullable final Metadata metadata) {
 
@@ -158,7 +158,7 @@ private static Thing removeACL(final Thing thing, final long nextRevision) {
                 .build();
     }
 
-    private Result<ThingEvent> handleModifyExistingWithV2Command(final Context<ThingId> context, final Thing thing,
+    private Result<ThingEvent<?>> handleModifyExistingWithV2Command(final Context<ThingId> context, final Thing thing,
             final Instant eventTs, final long nextRevision, final ModifyThing command,
             @Nullable final Metadata metadata) {
 
@@ -172,7 +172,7 @@ private Result<ThingEvent> handleModifyExistingWithV2Command(final Context<Thing
     /**
      * Handles a {@link ModifyThing} command that was sent via API v2 and targets a Thing with API version V1.
      */
-    private Result<ThingEvent> handleModifyExistingV1WithV2Command(final Context<ThingId> context,
+    private Result<ThingEvent<?>> handleModifyExistingV1WithV2Command(final Context<ThingId> context,
             final Thing thing, final Instant eventTs, final long nextRevision, final ModifyThing command,
             @Nullable final Metadata metadata) {
 
@@ -189,7 +189,7 @@ private Result<ThingEvent> handleModifyExistingV1WithV2Command(final Context<Thi
     /**
      * Handles a {@link ModifyThing} command that was sent via API v2 and targets a Thing with API version V2.
      */
-    private Result<ThingEvent> handleModifyExistingV2WithV2Command(final Context<ThingId> context,
+    private Result<ThingEvent<?>> handleModifyExistingV2WithV2Command(final Context<ThingId> context,
             final Thing thing, final Instant eventTs, final long nextRevision,
             final ModifyThing command, @Nullable final Metadata metadata) {
 
@@ -203,7 +203,7 @@ private Result<ThingEvent> handleModifyExistingV2WithV2Command(final Context<Thi
                 metadata);
     }
 
-    private Result<ThingEvent> applyModifyCommand(final Context<ThingId> context, final Thing thing,
+    private Result<ThingEvent<?>> applyModifyCommand(final Context<ThingId> context, final Thing thing,
             final Instant eventTs, final long nextRevision, final ModifyThing command,
             @Nullable final Metadata metadata) {
 
@@ -265,7 +265,7 @@ private static Thing copyPolicyId(final CommandStrategy.Context<ThingId> ctx, fi
     }
 
     @Override
-    public Result<ThingEvent> unhandled(final Context<ThingId> context, @Nullable final Thing thing,
+    public Result<ThingEvent<?>> unhandled(final Context<ThingId> context, @Nullable final Thing thing,
             final long nextRevision, final ModifyThing command) {
         return newErrorResult(new ThingNotAccessibleException(context.getState(), command.getDittoHeaders()), command);
     }
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAclEntryStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAclEntryStrategy.java
index 4af85735e5..d8b873bed8 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAclEntryStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAclEntryStrategy.java
@@ -45,7 +45,7 @@ final class RetrieveAclEntryStrategy extends AbstractThingCommandStrategy<Retrie
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrieveAclEntry command,
@@ -57,9 +57,9 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
 
         return extractAclEntry(command, thing)
                 .map(aclEntry -> {
-                    final WithDittoHeaders response = appendETagHeaderIfProvided(command,
+                    final WithDittoHeaders<?> response = appendETagHeaderIfProvided(command,
                             RetrieveAclEntryResponse.of(thingId, aclEntry, dittoHeaders), thing);
-                    return ResultFactory.<ThingEvent>newQueryResult(command, response);
+                    return ResultFactory.<ThingEvent<?>>newQueryResult(command, response);
                 })
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         ExceptionFactory.aclEntryNotFound(thingId, authorizationSubject, dittoHeaders), command));
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAclStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAclStrategy.java
index 8d299a9415..7a019bdbec 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAclStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAclStrategy.java
@@ -45,7 +45,7 @@ final class RetrieveAclStrategy extends AbstractThingCommandStrategy<RetrieveAcl
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrieveAcl command,
@@ -55,7 +55,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
                 .map(acl -> acl.toJson(command.getImplementedSchemaVersion()))
                 .orElseGet(JsonFactory::newObject);
 
-        final WithDittoHeaders response = appendETagHeaderIfProvided(command,
+        final WithDittoHeaders<?> response = appendETagHeaderIfProvided(command,
                 RetrieveAclResponse.of(context.getState(), aclJson, command.getDittoHeaders()), thing);
 
         return ResultFactory.newQueryResult(command, response);
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAttributeStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAttributeStrategy.java
index 1f4405b05c..dd586d7470 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAttributeStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAttributeStrategy.java
@@ -45,7 +45,7 @@ final class RetrieveAttributeStrategy extends AbstractThingCommandStrategy<Retri
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrieveAttribute command,
@@ -61,7 +61,7 @@ private Optional<Attributes> extractAttributes(final @Nullable Thing thing) {
         return getEntityOrThrow(thing).getAttributes();
     }
 
-    private Result<ThingEvent> getAttributeValueResult(final JsonObject attributes, final ThingId thingId,
+    private Result<ThingEvent<?>> getAttributeValueResult(final JsonObject attributes, final ThingId thingId,
             final RetrieveAttribute command, @Nullable final Thing thing) {
 
         final JsonPointer attributePointer = command.getAttributePointer();
@@ -69,7 +69,7 @@ private Result<ThingEvent> getAttributeValueResult(final JsonObject attributes,
 
         return attributes.getValue(attributePointer)
                 .map(value -> RetrieveAttributeResponse.of(thingId, attributePointer, value, dittoHeaders))
-                .<Result<ThingEvent>>map(response ->
+                .<Result<ThingEvent<?>>>map(response ->
                         ResultFactory.newQueryResult(command, appendETagHeaderIfProvided(command, response, thing)))
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         ExceptionFactory.attributeNotFound(thingId, attributePointer, dittoHeaders), command));
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAttributesStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAttributesStrategy.java
index 82778854a6..5a7aecef1a 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAttributesStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveAttributesStrategy.java
@@ -44,7 +44,7 @@ final class RetrieveAttributesStrategy extends AbstractThingCommandStrategy<Retr
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrieveAttributes command,
@@ -56,7 +56,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
         return extractAttributes(thing)
                 .map(attributes -> getAttributesJson(attributes, command))
                 .map(attributesJson -> RetrieveAttributesResponse.of(thingId, attributesJson, dittoHeaders))
-                .<Result<ThingEvent>>map(response ->
+                .<Result<ThingEvent<?>>>map(response ->
                         ResultFactory.newQueryResult(command, appendETagHeaderIfProvided(command, response, thing))
                 )
                 .orElseGet(() ->
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureDefinitionStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureDefinitionStrategy.java
index 3356f87a00..cdc71f0f56 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureDefinitionStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureDefinitionStrategy.java
@@ -43,7 +43,7 @@ final class RetrieveFeatureDefinitionStrategy extends AbstractThingCommandStrate
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrieveFeatureDefinition command,
@@ -63,7 +63,7 @@ private Optional<Feature> extractFeature(final RetrieveFeatureDefinition command
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getFeatureDefinition(final Feature feature, final ThingId thingId,
+    private Result<ThingEvent<?>> getFeatureDefinition(final Feature feature, final ThingId thingId,
             final RetrieveFeatureDefinition command, @Nullable final Thing thing) {
 
         final String featureId = feature.getId();
@@ -72,7 +72,7 @@ private Result<ThingEvent> getFeatureDefinition(final Feature feature, final Thi
         return feature.getDefinition()
                 .map(featureDefinition -> RetrieveFeatureDefinitionResponse.of(thingId, featureId,
                         featureDefinition, dittoHeaders))
-                .<Result<ThingEvent>>map(response ->
+                .<Result<ThingEvent<?>>>map(response ->
                         ResultFactory.newQueryResult(command, appendETagHeaderIfProvided(command, response, thing)))
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         ExceptionFactory.featureDefinitionNotFound(thingId, featureId, dittoHeaders), command));
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureDesiredPropertiesStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureDesiredPropertiesStrategy.java
index a54f6f6a79..818af85882 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureDesiredPropertiesStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureDesiredPropertiesStrategy.java
@@ -46,7 +46,7 @@ final class RetrieveFeatureDesiredPropertiesStrategy
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrieveFeatureDesiredProperties command,
@@ -68,7 +68,7 @@ private Optional<Feature> extractFeature(final RetrieveFeatureDesiredProperties
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getFeatureDesiredProperties(final Feature feature,
+    private Result<ThingEvent<?>> getFeatureDesiredProperties(final Feature feature,
             final ThingId thingId,
             final RetrieveFeatureDesiredProperties command,
             @Nullable final Thing thing) {
@@ -80,7 +80,7 @@ private Result<ThingEvent> getFeatureDesiredProperties(final Feature feature,
                 .map(desiredProperties -> getFeatureDesiredPropertiesJson(desiredProperties, command))
                 .map(desiredPropertiesJson -> RetrieveFeatureDesiredPropertiesResponse.of(thingId, featureId,
                         desiredPropertiesJson, dittoHeaders))
-                .<Result<ThingEvent>>map(response ->
+                .<Result<ThingEvent<?>>>map(response ->
                         ResultFactory.newQueryResult(command, appendETagHeaderIfProvided(command, response, thing)))
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         ExceptionFactory.featureDesiredPropertiesNotFound(thingId, featureId, dittoHeaders), command));
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureDesiredPropertyStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureDesiredPropertyStrategy.java
index 7b48e877e5..35a5e93013 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureDesiredPropertyStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureDesiredPropertyStrategy.java
@@ -46,7 +46,7 @@ final class RetrieveFeatureDesiredPropertyStrategy
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrieveFeatureDesiredProperty command,
@@ -68,7 +68,7 @@ private Optional<Feature> extractFeature(final RetrieveFeatureDesiredProperty co
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getRetrieveFeatureDesiredPropertyResult(final Feature feature,
+    private Result<ThingEvent<?>> getRetrieveFeatureDesiredPropertyResult(final Feature feature,
             final Context<ThingId> context,
             final RetrieveFeatureDesiredProperty command,
             @Nullable final Thing thing) {
@@ -81,7 +81,7 @@ private Result<ThingEvent> getRetrieveFeatureDesiredPropertyResult(final Feature
                                 command.getDittoHeaders()), command));
     }
 
-    private Result<ThingEvent> getRetrieveFeatureDesiredPropertyResult(final JsonObject featureProperties,
+    private Result<ThingEvent<?>> getRetrieveFeatureDesiredPropertyResult(final JsonObject featureProperties,
             final Context<ThingId> context,
             final RetrieveFeatureDesiredProperty command,
             @Nullable final Thing thing) {
@@ -93,7 +93,7 @@ private Result<ThingEvent> getRetrieveFeatureDesiredPropertyResult(final JsonObj
         return featureProperties.getValue(propertyPointer)
                 .map(featureDesiredProperty -> RetrieveFeatureDesiredPropertyResponse.of(context.getState(), featureId,
                         propertyPointer, featureDesiredProperty, dittoHeaders))
-                .<Result<ThingEvent>>map(response ->
+                .<Result<ThingEvent<?>>>map(response ->
                         ResultFactory.newQueryResult(command, appendETagHeaderIfProvided(command, response, thing)))
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         ExceptionFactory.featureDesiredPropertyNotFound(context.getState(), featureId, propertyPointer,
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeaturePropertiesStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeaturePropertiesStrategy.java
index 8c9931a1af..30c2c518f5 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeaturePropertiesStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeaturePropertiesStrategy.java
@@ -45,7 +45,7 @@ final class RetrieveFeaturePropertiesStrategy extends AbstractThingCommandStrate
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrieveFeatureProperties command,
@@ -65,7 +65,7 @@ private Optional<Feature> extractFeature(final RetrieveFeatureProperties command
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getFeatureProperties(final Feature feature, final ThingId thingId,
+    private Result<ThingEvent<?>> getFeatureProperties(final Feature feature, final ThingId thingId,
             final RetrieveFeatureProperties command, @Nullable final Thing thing) {
 
         final String featureId = feature.getId();
@@ -75,7 +75,7 @@ private Result<ThingEvent> getFeatureProperties(final Feature feature, final Thi
                 .map(featureProperties -> getFeaturePropertiesJson(featureProperties, command))
                 .map(featurePropertiesJson -> RetrieveFeaturePropertiesResponse.of(thingId, featureId,
                         featurePropertiesJson, dittoHeaders))
-                .<Result<ThingEvent>>map(response ->
+                .<Result<ThingEvent<?>>>map(response ->
                         ResultFactory.newQueryResult(command, appendETagHeaderIfProvided(command, response, thing)))
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         ExceptionFactory.featurePropertiesNotFound(thingId, featureId, dittoHeaders), command));
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeaturePropertyStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeaturePropertyStrategy.java
index 459b4693e2..25c93ad9a6 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeaturePropertyStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeaturePropertyStrategy.java
@@ -45,7 +45,7 @@ final class RetrieveFeaturePropertyStrategy extends AbstractThingCommandStrategy
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrieveFeatureProperty command,
@@ -65,7 +65,7 @@ private Optional<Feature> extractFeature(final RetrieveFeatureProperty command,
                 .flatMap(features -> features.getFeature(command.getFeatureId()));
     }
 
-    private Result<ThingEvent> getRetrieveFeaturePropertyResult(final Feature feature, final Context<ThingId> context,
+    private Result<ThingEvent<?>> getRetrieveFeaturePropertyResult(final Feature feature, final Context<ThingId> context,
             final RetrieveFeatureProperty command, @Nullable final Thing thing) {
 
         return feature.getProperties()
@@ -75,7 +75,7 @@ private Result<ThingEvent> getRetrieveFeaturePropertyResult(final Feature featur
                                 command.getDittoHeaders()), command));
     }
 
-    private Result<ThingEvent> getRetrieveFeaturePropertyResult(final JsonObject featureProperties,
+    private Result<ThingEvent<?>> getRetrieveFeaturePropertyResult(final JsonObject featureProperties,
             final Context<ThingId> context,
             final RetrieveFeatureProperty command, @Nullable final Thing thing) {
 
@@ -86,7 +86,7 @@ private Result<ThingEvent> getRetrieveFeaturePropertyResult(final JsonObject fea
         return featureProperties.getValue(propertyPointer)
                 .map(featureProperty -> RetrieveFeaturePropertyResponse.of(context.getState(), featureId,
                         propertyPointer, featureProperty, dittoHeaders))
-                .<Result<ThingEvent>>map(response ->
+                .<Result<ThingEvent<?>>>map(response ->
                         ResultFactory.newQueryResult(command, appendETagHeaderIfProvided(command, response, thing)))
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         ExceptionFactory.featurePropertyNotFound(context.getState(), featureId, propertyPointer,
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureStrategy.java
index 81fe40dd4c..38330e3149 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeatureStrategy.java
@@ -45,7 +45,7 @@ final class RetrieveFeatureStrategy extends AbstractThingCommandStrategy<Retriev
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrieveFeature command,
@@ -63,7 +63,7 @@ private Optional<Features> extractFeatures(final @Nullable Thing thing) {
         return getEntityOrThrow(thing).getFeatures();
     }
 
-    private Result<ThingEvent> getFeatureResult(final Features features, final ThingId thingId,
+    private Result<ThingEvent<?>> getFeatureResult(final Features features, final ThingId thingId,
             final RetrieveFeature command, @Nullable final Thing thing) {
 
         final String featureId = command.getFeatureId();
@@ -72,7 +72,7 @@ private Result<ThingEvent> getFeatureResult(final Features features, final Thing
         return features.getFeature(featureId)
                 .map(feature -> getFeatureJson(feature, command))
                 .map(featureJson -> RetrieveFeatureResponse.of(thingId, featureId, featureJson, dittoHeaders))
-                .<Result<ThingEvent>>map(response ->
+                .<Result<ThingEvent<?>>>map(response ->
                         ResultFactory.newQueryResult(command, appendETagHeaderIfProvided(command, response, thing)))
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         ExceptionFactory.featureNotFound(thingId, featureId, dittoHeaders), command));
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeaturesStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeaturesStrategy.java
index f39edcc7b8..5c84b277f1 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeaturesStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveFeaturesStrategy.java
@@ -44,7 +44,7 @@ final class RetrieveFeaturesStrategy extends AbstractThingCommandStrategy<Retrie
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrieveFeatures command,
@@ -56,7 +56,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
         return extractFeatures(thing)
                 .map(features -> getFeaturesJson(features, command))
                 .map(featuresJson -> RetrieveFeaturesResponse.of(thingId, featuresJson, dittoHeaders))
-                .<Result<ThingEvent>>map(response ->
+                .<Result<ThingEvent<?>>>map(response ->
                         ResultFactory.newQueryResult(command, appendETagHeaderIfProvided(command, response, thing)))
                 .orElseGet(() -> ResultFactory
                         .newErrorResult(ExceptionFactory.featuresNotFound(thingId, dittoHeaders), command));
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrievePolicyIdStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrievePolicyIdStrategy.java
index 944c6e383b..293e1d81c5 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrievePolicyIdStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrievePolicyIdStrategy.java
@@ -43,7 +43,7 @@ final class RetrievePolicyIdStrategy extends AbstractThingCommandStrategy<Retrie
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrievePolicyId command,
@@ -52,7 +52,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
         return extractPolicyId(thing)
                 .map(policyId -> RetrievePolicyIdResponse.of(context.getState(), policyId,
                         command.getDittoHeaders()))
-                .<Result<ThingEvent>>map(response ->
+                .<Result<ThingEvent<?>>>map(response ->
                         ResultFactory.newQueryResult(command, appendETagHeaderIfProvided(command, response, thing)))
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         PolicyIdNotAccessibleException.newBuilder(context.getState())
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveThingDefinitionStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveThingDefinitionStrategy.java
index c78055d8bb..78eb9a4493 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveThingDefinitionStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveThingDefinitionStrategy.java
@@ -44,7 +44,7 @@ final class RetrieveThingDefinitionStrategy extends AbstractThingCommandStrategy
 
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrieveThingDefinition command,
@@ -53,7 +53,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
         return extractDefinition(thing)
                 .map(definition -> RetrieveThingDefinitionResponse.of(context.getState(), definition,
                         command.getDittoHeaders()))
-                .<Result<ThingEvent>>map(response ->
+                .<Result<ThingEvent<?>>>map(response ->
                         ResultFactory.newQueryResult(command, appendETagHeaderIfProvided(command, response, thing)))
                 .orElseGet(() -> ResultFactory.newErrorResult(
                         ThingDefinitionNotAccessibleException.newBuilder(context.getState())
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveThingStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveThingStrategy.java
index 8e2a1fa6a9..108b518bd5 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveThingStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/RetrieveThingStrategy.java
@@ -56,7 +56,7 @@ public boolean isDefined(final Context<ThingId> context, @Nullable final Thing t
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final RetrieveThing command,
@@ -66,7 +66,7 @@ protected Result<ThingEvent> doApply(final Context<ThingId> context,
                 appendETagHeaderIfProvided(command, getRetrieveThingResponse(thing, command), thing));
     }
 
-    private static WithDittoHeaders getRetrieveThingResponse(@Nullable final Thing thing,
+    private static WithDittoHeaders<?> getRetrieveThingResponse(@Nullable final Thing thing,
             final ThingQueryCommand<RetrieveThing> command) {
         if (thing != null) {
             return RetrieveThingResponse.of(command.getThingEntityId(), getThingJson(thing, command),
@@ -87,7 +87,7 @@ private static ThingNotAccessibleException notAccessible(final ThingQueryCommand
     }
 
     @Override
-    public Result<ThingEvent> unhandled(final Context<ThingId> context, @Nullable final Thing thing,
+    public Result<ThingEvent<?>> unhandled(final Context<ThingId> context, @Nullable final Thing thing,
             final long nextRevision, final RetrieveThing command) {
         return ResultFactory.newErrorResult(
                 new ThingNotAccessibleException(context.getState(), command.getDittoHeaders()), command);
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/SudoRetrieveThingStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/SudoRetrieveThingStrategy.java
index 811b87c4e8..93f585b005 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/SudoRetrieveThingStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/SudoRetrieveThingStrategy.java
@@ -56,7 +56,7 @@ public boolean isDefined(final Context<ThingId> context, @Nullable final Thing t
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final SudoRetrieveThing command,
@@ -81,7 +81,7 @@ private static JsonSchemaVersion determineSchemaVersion(final SudoRetrieveThing
     }
 
     @Override
-    public Result<ThingEvent> unhandled(final Context<ThingId> context, @Nullable final Thing thing,
+    public Result<ThingEvent<?>> unhandled(final Context<ThingId> context, @Nullable final Thing thing,
             final long nextRevision, final SudoRetrieveThing command) {
         return ResultFactory.newErrorResult(
                 new ThingNotAccessibleException(context.getState(), command.getDittoHeaders()), command);
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ThingCommandStrategies.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ThingCommandStrategies.java
index c42d493ebb..ad16ccd5a1 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ThingCommandStrategies.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ThingCommandStrategies.java
@@ -26,7 +26,7 @@
  * The collection of the command strategies of {@code ThingPersistenceActor}.
  */
 public final class ThingCommandStrategies
-        extends AbstractCommandStrategies<Command, Thing, ThingId, Result<ThingEvent>> {
+        extends AbstractCommandStrategies<Command<?>, Thing, ThingId, Result<ThingEvent<?>>> {
 
     private static final ThingCommandStrategies INSTANCE = new ThingCommandStrategies();
 
@@ -61,7 +61,7 @@ public static ThingCommandStrategies getInstance() {
      *
      * @return the instance.
      */
-    public static CommandStrategy<CreateThing, Thing, ThingId, Result<ThingEvent>> getCreateThingStrategy() {
+    public static CommandStrategy<CreateThing, Thing, ThingId, Result<ThingEvent<?>>> getCreateThingStrategy() {
         return CreateThingStrategy.getInstance();
     }
 
@@ -138,7 +138,7 @@ private void addSudoStrategies() {
     }
 
     @Override
-    protected Result<ThingEvent> getEmptyResult() {
+    protected Result<ThingEvent<?>> getEmptyResult() {
         return ResultFactory.emptyResult();
     }
 }
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ThingConflictStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ThingConflictStrategy.java
index c765d6b688..14a753839b 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ThingConflictStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ThingConflictStrategy.java
@@ -58,7 +58,7 @@ protected Optional<Metadata> calculateRelativeMetadata(@Nullable final Thing ent
     }
 
     @Override
-    protected Result<ThingEvent> doApply(final Context<ThingId> context,
+    protected Result<ThingEvent<?>> doApply(final Context<ThingId> context,
             @Nullable final Thing thing,
             final long nextRevision,
             final CreateThing command,
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/events/AbstractThingEventStrategy.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/events/AbstractThingEventStrategy.java
index 74e752ccea..60afaf11c1 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/events/AbstractThingEventStrategy.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/events/AbstractThingEventStrategy.java
@@ -83,7 +83,7 @@ private Metadata mergeMetadata(@Nullable final Thing thing, final T event) {
      * Apply the specified event to the also specified ThingBuilder.
      * The builder has already the specified revision set as well as the event's timestamp.
      *
-     * @param event the ThingEvent to be applied.
+     * @param event the ThingEvent<?>to be applied.
      * @param thingBuilder builder which is derived from the {@code event}'s Thing with the revision and event
      * timestamp already set.
      * @return the updated {@code thingBuilder} after applying {@code event}.
diff --git a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/events/ThingEventStrategies.java b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/events/ThingEventStrategies.java
index 11317ec04f..092ce6da19 100644
--- a/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/events/ThingEventStrategies.java
+++ b/services/things/persistence/src/main/java/org/eclipse/ditto/services/things/persistence/actors/strategies/events/ThingEventStrategies.java
@@ -61,7 +61,7 @@
  * This Singleton strategy handles all {@link org.eclipse.ditto.signals.events.things.ThingEvent}s.
  */
 @Immutable
-public final class ThingEventStrategies extends AbstractEventStrategies<ThingEvent, Thing> {
+public final class ThingEventStrategies extends AbstractEventStrategies<ThingEvent<?>, Thing> {
 
     private static final ThingEventStrategies INSTANCE = new ThingEventStrategies();
 
diff --git a/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/PersistenceActorTestBaseWithSnapshotting.java b/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/PersistenceActorTestBaseWithSnapshotting.java
index bcec40f549..1d754cde30 100644
--- a/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/PersistenceActorTestBaseWithSnapshotting.java
+++ b/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/PersistenceActorTestBaseWithSnapshotting.java
@@ -77,10 +77,10 @@ public abstract class PersistenceActorTestBaseWithSnapshotting extends Persisten
     private static final String ACTIVITY_CHECK_DELETED_INTERVAL = ACTIVITY_CHECK_PREFIX + "deleted-interval";
 
     private ThingMongoEventAdapter eventAdapter;
-    private ThingsJournalTestHelper<ThingEvent> journalTestHelper;
+    private ThingsJournalTestHelper<ThingEvent<?>> journalTestHelper;
     private ThingsSnapshotTestHelper<Thing> snapshotTestHelper;
 
-    private Map<Class<? extends Command>, BiFunction<Command, Thing, ThingEvent>> commandToEventMapperRegistry;
+    private Map<Class<? extends Command<?>>, BiFunction<Command<?>, Thing, ThingEvent<?>>> commandToEventMapperRegistry;
 
     Config createNewDefaultTestConfig() {
         return ConfigFactory.empty()
@@ -130,7 +130,7 @@ protected void setup(final Config customConfig) {
         commandToEventMapperRegistry.put(DeleteThing.class, (command, thing) -> {
             final DeleteThing deleteCommand = (DeleteThing) command;
             return ThingDeleted.of(deleteCommand.getThingEntityId(),
-                    thing.getRevision().get().toLong(),
+                    thing.getRevision().orElseThrow().toLong(),
                     thing.getModified().orElse(null),
                     DittoHeaders.empty(),
                     thing.getMetadata().orElse(null));
@@ -165,9 +165,9 @@ void assertSnapshotsEmpty(final ThingId thingId) {
         assertSnapshots(thingId, Collections.emptyList());
     }
 
-    void assertJournal(final ThingId thingId, final List<Event> expectedEvents) {
+    void assertJournal(final ThingId thingId, final List<Event<?>> expectedEvents) {
         retryOnAssertionError(() -> {
-            final List<ThingEvent> actualEvents = journalTestHelper.getAllEvents(thingId);
+            final List<ThingEvent<?>> actualEvents = journalTestHelper.getAllEvents(thingId);
             Assertions.assertListWithIndexInfo(actualEvents, (actual, expected) -> {
                 assertThat(actual)
                         .hasType(expected.getType())
@@ -191,11 +191,11 @@ static Thing toDeletedThing(final Thing thing, final int newRevision) {
         return thing.toBuilder().setRevision(newRevision).setLifecycle(ThingLifecycle.DELETED).build();
     }
 
-    Event toEvent(final Command command, final Thing templateThing) {
-        final Class<? extends Command> clazz = command.getClass();
-        final BiFunction<Command, Thing, ThingEvent> commandToEventFunction = commandToEventMapperRegistry.get(clazz);
+    Event<?> toEvent(final Command<?> command, final Thing templateThing) {
+        final BiFunction<Command<?>, Thing, ThingEvent<?>> commandToEventFunction =
+                commandToEventMapperRegistry.get(command.getClass());
         if (commandToEventFunction == null) {
-            throw new UnsupportedOperationException("Mapping not yet implemented for type: " + clazz);
+            throw new UnsupportedOperationException("Mapping not yet implemented for type: " + command.getClass());
         }
 
         return commandToEventFunction.apply(command, templateThing);
@@ -214,8 +214,8 @@ private static void retryOnAssertionError(final Runnable r) {
         Assertions.retryOnAssertionError(r, PERSISTENCE_ASSERT_WAIT_AT_MOST_MS, PERSISTENCE_ASSERT_RETRY_DELAY_MS);
     }
 
-    private ThingEvent convertJournalEntryToEvent(final BsonDocument dbObject, final long sequenceNumber) {
-        final ThingEvent<?> head = (ThingEvent) eventAdapter.fromJournal(dbObject, null).events().head();
+    private ThingEvent<?> convertJournalEntryToEvent(final BsonDocument dbObject, final long sequenceNumber) {
+        final ThingEvent<?> head = (ThingEvent<?>) eventAdapter.fromJournal(dbObject, null).events().head();
         return head.setRevision(sequenceNumber);
     }
 
diff --git a/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/ThingPersistenceActorCleanupTest.java b/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/ThingPersistenceActorCleanupTest.java
index 2f7028de2d..dcde8f7983 100644
--- a/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/ThingPersistenceActorCleanupTest.java
+++ b/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/ThingPersistenceActorCleanupTest.java
@@ -58,7 +58,7 @@ public final class ThingPersistenceActorCleanupTest extends PersistenceActorTest
     @Test
     public void cleanupDeletesUntilButExcludingLatestSnapshot() {
         setup(createNewDefaultTestConfig());
-        final List<Event> expectedEvents = new ArrayList<>();
+        final List<Event<?>> expectedEvents = new ArrayList<>();
         final LinkedList<Thing> expectedSnapshots = new LinkedList<>();
 
         new TestKit(actorSystem) {
@@ -117,13 +117,13 @@ public void cleanupDeletesUntilButExcludingLatestSnapshot() {
 
                 // only events after the latest snapshot should survive
                 final long revision = latestSnapshot;
-                final List<Event> expectedEventsAfterCleanup = expectedEvents.stream()
+                final List<Event<?>> expectedEventsAfterCleanup = expectedEvents.stream()
                         .filter(e -> e.getRevision() > revision)
                         .collect(Collectors.toList());
                 assertJournal(thingId, expectedEventsAfterCleanup);
             }
 
-            private Event sendModifyThing(final Thing modifiedThing, final ActorRef underTest,
+            private Event<?> sendModifyThing(final Thing modifiedThing, final ActorRef underTest,
                     final int revisionNumber) {
                 final ModifyThing modifyThingCommand =
                         ModifyThing.of(modifiedThing.getEntityId()
@@ -141,7 +141,7 @@ private Event sendModifyThing(final Thing modifiedThing, final ActorRef underTes
     @Test
     public void testDeletedThingIsCleanedUpCorrectly() {
         setup(createNewDefaultTestConfig());
-        final List<Event> expectedEvents = new ArrayList<>();
+        final List<Event<?>> expectedEvents = new ArrayList<>();
 
         new TestKit(actorSystem) {
             {
@@ -170,7 +170,7 @@ public void testDeletedThingIsCleanedUpCorrectly() {
 
                 final Thing expectedDeletedSnapshot = toDeletedThing(thingCreated, 2);
                 assertSnapshots(thingId, Collections.singletonList(expectedDeletedSnapshot));
-                final Event deletedEvent = toEvent(deleteThing, expectedDeletedSnapshot);
+                final Event<?> deletedEvent = toEvent(deleteThing, expectedDeletedSnapshot);
                 expectedEvents.add(deletedEvent);
                 assertJournal(thingId, expectedEvents);
 
diff --git a/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/ThingPersistenceActorSnapshottingTest.java b/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/ThingPersistenceActorSnapshottingTest.java
index 228e26b4a0..6dfdc7f701 100755
--- a/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/ThingPersistenceActorSnapshottingTest.java
+++ b/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/ThingPersistenceActorSnapshottingTest.java
@@ -87,7 +87,7 @@ public void deletedThingIsSnapshotWithCorrectDataAndCanBeRecreated() {
                         .orElseThrow(IllegalStateException::new);
                 assertThingInResponse(thingCreated, thing, 1);
 
-                final Event expectedCreatedEvent = toEvent(createThing, thingCreated);
+                final Event<?> expectedCreatedEvent = toEvent(createThing, thingCreated);
                 assertJournal(thingId, Collections.singletonList(expectedCreatedEvent));
                 assertSnapshotsEmpty(thingId);
 
@@ -97,7 +97,7 @@ public void deletedThingIsSnapshotWithCorrectDataAndCanBeRecreated() {
 
                 final Thing expectedDeletedSnapshot = toDeletedThing(thingCreated, 2);
                 assertSnapshots(thingId, Collections.singletonList(expectedDeletedSnapshot));
-                final Event expectedDeletedEvent = toEvent(deleteThing, expectedDeletedSnapshot);
+                final Event<?> expectedDeletedEvent = toEvent(deleteThing, expectedDeletedSnapshot);
                 // created-event has been deleted due to snapshot
                 assertJournal(thingId, Arrays.asList(expectedCreatedEvent, expectedDeletedEvent));
 
@@ -123,7 +123,7 @@ public void deletedThingIsSnapshotWithCorrectDataAndCanBeRecreated() {
                 final Thing actualThing = reCreateThingResponse.getThingCreated().orElse(null);
                 assertThingInResponse(actualThing, thing, 3);
 
-                final Event expectedReCreatedEvent = toEvent(createThing, actualThing);
+                final Event<?> expectedReCreatedEvent = toEvent(createThing, actualThing);
                 assertJournal(thingId,
                         Arrays.asList(expectedCreatedEvent, expectedDeletedEvent, expectedReCreatedEvent));
                 assertSnapshots(thingId, Collections.singletonList(expectedDeletedSnapshot));
@@ -164,7 +164,7 @@ public void thingInArbitraryStateIsSnapshotCorrectly() {
 
                 LOGGER.info("Expecting Event made it to Journal and snapshots are empty. ..");
 
-                final Event expectedCreatedEvent = toEvent(createThing, actualThing);
+                final Event<?> expectedCreatedEvent = toEvent(createThing, actualThing);
                 assertJournal(thingId, Collections.singletonList(expectedCreatedEvent));
                 assertSnapshotsEmpty(thingId);
 
@@ -182,7 +182,7 @@ public void thingInArbitraryStateIsSnapshotCorrectly() {
 
                 LOGGER.info("Expecting Event made it to Journal and snapshots contain Thing..");
 
-                final Event expectedModifiedEvent = toEvent(modifyThing, thingForModify);
+                final Event<?> expectedModifiedEvent = toEvent(modifyThing, thingForModify);
                 assertJournal(thingId, Arrays.asList(expectedCreatedEvent, expectedModifiedEvent));
                 assertSnapshots(thingId, Collections.singletonList(thingForModify));
 
diff --git a/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/AbstractCommandStrategyTest.java b/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/AbstractCommandStrategyTest.java
index c6d01c8058..ee1066c3f5 100644
--- a/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/AbstractCommandStrategyTest.java
+++ b/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/AbstractCommandStrategyTest.java
@@ -66,68 +66,70 @@ protected static CommandStrategy.Context<ThingId> getDefaultContext() {
         return DefaultContext.getInstance(THING_ID, logger);
     }
 
-    protected static <T extends ThingModifiedEvent<?>> T assertModificationResult(final CommandStrategy underTest,
+    protected static <C extends Command<?>, T extends ThingModifiedEvent<?>> T assertModificationResult(
+            final CommandStrategy<C, Thing, ThingId, Result<ThingEvent<?>>> underTest,
             @Nullable final Thing thing,
-            final Command command,
+            final C command,
             final Class<T> expectedEventClass,
-            final CommandResponse expectedCommandResponse) {
+            final CommandResponse<?> expectedCommandResponse) {
 
         return assertModificationResult(underTest, thing, command, expectedEventClass, expectedCommandResponse, false);
     }
 
-    protected static <T extends ThingModifiedEvent<?>> T assertModificationResult(final CommandStrategy underTest,
+    protected static <C extends Command<?>, T extends ThingModifiedEvent<?>> T assertModificationResult(
+            final CommandStrategy<C, Thing, ThingId, Result<ThingEvent<?>>> underTest,
             @Nullable final Thing thing,
-            final Command command,
+            final C command,
             final Class<T> expectedEventClass,
-            final CommandResponse expectedCommandResponse,
+            final CommandResponse<?> expectedCommandResponse,
             final boolean becomeDeleted) {
 
         final CommandStrategy.Context<ThingId> context = getDefaultContext();
-        final Result<ThingEvent> result = applyStrategy(underTest, context, thing, command);
+        final Result<ThingEvent<?>> result = applyStrategy(underTest, context, thing, command);
 
         return assertModificationResult(result, expectedEventClass, expectedCommandResponse, becomeDeleted);
     }
 
-    protected static <C extends Command> void assertErrorResult(
-            final CommandStrategy<C, Thing, ThingId, Result<ThingEvent>> underTest,
+    protected static <C extends Command<?>> void assertErrorResult(
+            final CommandStrategy<C, Thing, ThingId, Result<ThingEvent<?>>> underTest,
             @Nullable final Thing thing,
             final C command,
             final DittoRuntimeException expectedException) {
 
-        final ResultVisitor<ThingEvent> mock = mock(Dummy.class);
+        final ResultVisitor<ThingEvent<?>> mock = mock(Dummy.class);
         applyStrategy(underTest, getDefaultContext(), thing, command).accept(mock);
         verify(mock).onError(eq(expectedException), eq(command));
     }
 
-    protected static <C extends Command> void assertQueryResult(
-            final CommandStrategy<C, Thing, ThingId, Result<ThingEvent>> underTest,
+    protected static <C extends Command<?>> void assertQueryResult(
+            final CommandStrategy<C, Thing, ThingId, Result<ThingEvent<?>>> underTest,
             @Nullable final Thing thing,
             final C command,
-            final CommandResponse expectedCommandResponse) {
+            final CommandResponse<?> expectedCommandResponse) {
 
         assertInfoResult(applyStrategy(underTest, getDefaultContext(), thing, command), expectedCommandResponse);
     }
 
 
-    protected static <C extends Command> void assertUnhandledResult(
-            final AbstractCommandStrategy<C, Thing, ThingId, Result<ThingEvent>> underTest,
+    protected static <C extends Command<?>> void assertUnhandledResult(
+            final AbstractCommandStrategy<C, Thing, ThingId, Result<ThingEvent<?>>> underTest,
             @Nullable final Thing thing,
             final C command,
             final DittoRuntimeException expectedResponse) {
 
-        final ResultVisitor<ThingEvent> mock = mock(Dummy.class);
+        final ResultVisitor<ThingEvent<?>> mock = mock(Dummy.class);
         underTest.unhandled(getDefaultContext(), thing, NEXT_REVISION, command).accept(mock);
         verify(mock).onError(eq(expectedResponse), eq(command));
     }
 
-    private static <T extends ThingModifiedEvent<?>> T assertModificationResult(final Result<ThingEvent> result,
+    private static <T extends ThingModifiedEvent<?>> T assertModificationResult(final Result<ThingEvent<?>> result,
             final Class<T> eventClazz,
-            final WithDittoHeaders expectedResponse,
+            final WithDittoHeaders<?> expectedResponse,
             final boolean becomeDeleted) {
 
         final ArgumentCaptor<T> event = ArgumentCaptor.forClass(eventClazz);
 
-        final ResultVisitor<ThingEvent> mock = mock(Dummy.class);
+        final ResultVisitor<ThingEvent<?>> mock = mock(Dummy.class);
 
         result.accept(mock);
 
@@ -136,14 +138,14 @@ private static <T extends ThingModifiedEvent<?>> T assertModificationResult(fina
         return event.getValue();
     }
 
-    private static void assertInfoResult(final Result<ThingEvent> result, final WithDittoHeaders infoResponse) {
-        final ResultVisitor<ThingEvent> mock = mock(Dummy.class);
+    private static void assertInfoResult(final Result<ThingEvent<?>> result, final WithDittoHeaders<?> infoResponse) {
+        final ResultVisitor<ThingEvent<?>> mock = mock(Dummy.class);
         result.accept(mock);
         verify(mock).onQuery(any(), eq(infoResponse));
     }
 
-    private static <C extends Command> Result<ThingEvent> applyStrategy(
-            final CommandStrategy<C, Thing, ThingId, Result<ThingEvent>> underTest,
+    private static <C extends Command<?>> Result<ThingEvent<?>> applyStrategy(
+            final CommandStrategy<C, Thing, ThingId, Result<ThingEvent<?>>> underTest,
             final CommandStrategy.Context<ThingId> context,
             final @Nullable Thing thing,
             final C command) {
@@ -151,6 +153,6 @@ private static <C extends Command> Result<ThingEvent> applyStrategy(
         return underTest.apply(context, thing, NEXT_REVISION, command);
     }
 
-    interface Dummy extends ResultVisitor<ThingEvent> {}
+    interface Dummy extends ResultVisitor<ThingEvent<?>> {}
 
 }
diff --git a/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ResultFactoryTest.java b/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ResultFactoryTest.java
index 9987f8c303..9a89740d15 100644
--- a/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ResultFactoryTest.java
+++ b/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ResultFactoryTest.java
@@ -36,7 +36,7 @@
  */
 public final class ResultFactoryTest {
 
-    private final ResultVisitor<ThingEvent> mock = mock(Dummy.class);
+    private final ResultVisitor<ThingEvent<?>> mock = mock(Dummy.class);
     private final ThingQueryCommand thingQueryCommand = mock(ThingQueryCommand.class);
     private final ThingModifyCommand thingModifyCommand = mock(ThingModifyCommand.class);
     private final ThingModifiedEvent thingModifiedEvent = mock(ThingModifiedEvent.class);
@@ -50,7 +50,7 @@ public void assertImmutability() {
 
     @Test
     public void notifyQueryResponse() {
-        final Result<ThingEvent> result = ResultFactory.newQueryResult(thingQueryCommand, response);
+        final Result<ThingEvent<?>> result = ResultFactory.newQueryResult(thingQueryCommand, response);
         result.accept(mock);
         verify(mock).onQuery(eq(thingQueryCommand), eq(response));
     }
@@ -58,7 +58,7 @@ public void notifyQueryResponse() {
     @Test
     public void notifyException() {
         final Command command = mock(Command.class);
-        final Result<ThingEvent> result = ResultFactory.newErrorResult(exception, command);
+        final Result<ThingEvent<?>> result = ResultFactory.newErrorResult(exception, command);
         result.accept(this.mock);
         verify(this.mock).onError(eq(exception), eq(command));
     }
@@ -79,7 +79,7 @@ public void notifyMutationResponseWithBecomingDeleted() {
     }
 
     private void assertNotifyMutationResponse(final boolean becomeCreated, final boolean becomeDeleted) {
-        final Result<ThingEvent> result =
+        final Result<ThingEvent<?>> result =
                 ResultFactory.newMutationResult(thingModifyCommand, thingModifiedEvent, response, becomeCreated,
                         becomeDeleted);
         result.accept(mock);
@@ -87,7 +87,7 @@ private void assertNotifyMutationResponse(final boolean becomeCreated, final boo
                 eq(becomeDeleted));
     }
 
-    interface Dummy extends ResultVisitor<ThingEvent> {
+    interface Dummy extends ResultVisitor<ThingEvent<?>> {
     }
 
 }
diff --git a/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ThingConflictStrategyTest.java b/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ThingConflictStrategyTest.java
index f18ba955e3..ba31717cab 100644
--- a/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ThingConflictStrategyTest.java
+++ b/services/things/persistence/src/test/java/org/eclipse/ditto/services/things/persistence/actors/strategies/commands/ThingConflictStrategyTest.java
@@ -56,7 +56,7 @@ public void createConflictResultWithoutPrecondition() {
         final Thing thing = ThingsModelFactory.newThingBuilder().setId(thingId).setRevision(25L).build();
         final CommandStrategy.Context<ThingId> context = DefaultContext.getInstance(thingId, mockLoggingAdapter());
         final CreateThing command = CreateThing.of(thing, null, DittoHeaders.empty());
-        final Result<ThingEvent> result = underTest.apply(context, thing, 26L, command);
+        final Result<ThingEvent<?>> result = underTest.apply(context, thing, 26L, command);
         result.accept(new ExpectErrorVisitor(ThingConflictException.class));
     }
 
@@ -69,7 +69,7 @@ public void createPreconditionFailedResultWithPrecondition() {
         final CreateThing command = CreateThing.of(thing, null, DittoHeaders.newBuilder()
                 .ifNoneMatch(EntityTagMatchers.fromStrings("*"))
                 .build());
-        final Result<ThingEvent> result = underTest.apply(context, thing, 26L, command);
+        final Result<ThingEvent<?>> result = underTest.apply(context, thing, 26L, command);
         result.accept(new ExpectErrorVisitor(ThingPreconditionFailedException.class));
     }
 
@@ -79,7 +79,7 @@ private static DittoDiagnosticLoggingAdapter mockLoggingAdapter() {
         return mock;
     }
 
-    private static final class ExpectErrorVisitor implements ResultVisitor<ThingEvent> {
+    private static final class ExpectErrorVisitor implements ResultVisitor<ThingEvent<?>> {
 
         private final Class<? extends DittoRuntimeException> clazz;
 
@@ -88,13 +88,13 @@ private ExpectErrorVisitor(final Class<? extends DittoRuntimeException> clazz) {
         }
 
         @Override
-        public void onMutation(final Command command, final ThingEvent event, final WithDittoHeaders response,
+        public void onMutation(final Command<?> command, final ThingEvent<?> event, final WithDittoHeaders<?> response,
                 final boolean becomeCreated, final boolean becomeDeleted) {
             throw new AssertionError("Expect error, got mutation: " + event);
         }
 
         @Override
-        public void onQuery(final Command command, final WithDittoHeaders response) {
+        public void onQuery(final Command<?> command, final WithDittoHeaders<?> response) {
             throw new AssertionError("Expect error, got query: " + response);
         }
 
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/AbstractPersistenceSupervisor.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/AbstractPersistenceSupervisor.java
index 0d2f23c9dc..a6a1c0faef 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/AbstractPersistenceSupervisor.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/AbstractPersistenceSupervisor.java
@@ -52,10 +52,9 @@ public abstract class AbstractPersistenceSupervisor<E extends EntityId> extends
 
     @Nullable private E entityId;
     @Nullable private Props persistenceActorProps;
-    @Nullable private ShutdownBehaviour shutdownBehaviour;
     @Nullable private ActorRef child;
 
-    private ExponentialBackOffConfig exponentialBackOffConfig;
+    private final ExponentialBackOffConfig exponentialBackOffConfig;
     private Instant lastRestart;
     private Duration restartDelay;
 
@@ -123,9 +122,8 @@ public void preStart() throws Exception {
         try {
             entityId = getEntityId();
             persistenceActorProps = getPersistenceActorProps(entityId);
-            shutdownBehaviour = getShutdownBehaviour(entityId);
             startChild(Control.START_CHILD);
-            becomeActive(shutdownBehaviour);
+            becomeActive(getShutdownBehaviour(entityId));
         } catch (final Exception e) {
             log.error(e, "Failed to determine entity ID; becoming corrupted.");
             becomeCorrupted();
@@ -252,7 +250,7 @@ private void replyUnavailableException(final Object message) {
         log.warning("Received message during downtime of child actor for Entity with ID <{}>: <{}>", entityId, message);
         final DittoRuntimeExceptionBuilder<?> builder = getUnavailableExceptionBuilder(entityId);
         if (message instanceof WithDittoHeaders) {
-            builder.dittoHeaders(((WithDittoHeaders) message).getDittoHeaders());
+            builder.dittoHeaders(((WithDittoHeaders<?>) message).getDittoHeaders());
         }
         getSender().tell(builder.build(), getSelf());
     }
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/AbstractShardedPersistenceActor.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/AbstractShardedPersistenceActor.java
index 2a7c9516a0..a621bfa668 100755
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/AbstractShardedPersistenceActor.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/AbstractShardedPersistenceActor.java
@@ -56,11 +56,11 @@
  * @param <E> the base type of the Events this actor emits
  */
 public abstract class AbstractShardedPersistenceActor<
-        C extends Command,
+        C extends Command<?>,
         S,
         I extends EntityId,
         K,
-        E extends Event> extends AbstractPersistentActorWithTimersAndCleanup implements ResultVisitor<E> {
+        E extends Event<? extends E>> extends AbstractPersistentActorWithTimersAndCleanup implements ResultVisitor<E> {
 
     private final SnapshotAdapter<S> snapshotAdapter;
     private final Receive handleEvents;
@@ -87,6 +87,7 @@ public abstract class AbstractShardedPersistenceActor<
      * @param entityId the entity ID.
      * @param snapshotAdapter the entity's snapshot adapter.
      */
+    @SuppressWarnings("unchecked")
     protected AbstractShardedPersistenceActor(final I entityId, final SnapshotAdapter<S> snapshotAdapter) {
         this.entityId = entityId;
         this.snapshotAdapter = snapshotAdapter;
@@ -97,7 +98,7 @@ protected AbstractShardedPersistenceActor(final I entityId, final SnapshotAdapte
 
         handleEvents = ReceiveBuilder.create()
                 .match(getEventClass(), event -> {
-                    entity = getEventStrategy().handle(event, entity, getRevisionNumber());
+                    entity = getEventStrategy().handle((E) event, entity, getRevisionNumber());
                     onEntityModified();
                 })
                 .build();
@@ -124,7 +125,7 @@ protected void onEntityModified() {
     /**
      * @return class of the events persisted by this actor.
      */
-    protected abstract Class<E> getEventClass();
+    protected abstract Class<?> getEventClass();
 
     /**
      * @return the context for handling commands based on the actor's current state.
@@ -166,7 +167,7 @@ protected void onEntityModified() {
     /**
      * @return An exception builder to respond to unexpected commands addressed to a nonexistent entity.
      */
-    protected abstract DittoRuntimeExceptionBuilder newNotAccessibleExceptionBuilder();
+    protected abstract DittoRuntimeExceptionBuilder<?> newNotAccessibleExceptionBuilder();
 
     /**
      * Publish an event.
@@ -293,7 +294,7 @@ protected void persistAndApplyEvent(final E event, final BiConsumer<E, S> handle
             final DittoHeaders newHeaders = event.getDittoHeaders().toBuilder()
                     .schemaVersion(getEntitySchemaVersion(entity))
                     .build();
-            modifiedEvent = (E) event.setDittoHeaders(newHeaders);
+            modifiedEvent = event.setDittoHeaders(newHeaders);
         } else {
             modifiedEvent = event;
         }
@@ -381,13 +382,13 @@ private void handleByCommandStrategy(final C command) {
         handleByStrategy(command, getCreatedStrategy());
     }
 
-    private <T extends Command> ReceiveBuilder handleByStrategyReceiveBuilder(
+    private <T extends Command<?>> ReceiveBuilder handleByStrategyReceiveBuilder(
             final CommandStrategy<T, S, K, Result<E>> strategy) {
         return ReceiveBuilder.create()
                 .match(strategy.getMatchingClass(), command -> handleByStrategy(command, strategy));
     }
 
-    private <T extends Command> void handleByStrategy(final T command,
+    private <T extends Command<?>> void handleByStrategy(final T command,
             final CommandStrategy<T, S, K, Result<E>> strategy) {
         log.debug("Handling by strategy: <{}>", command);
         accessCounter++;
@@ -402,7 +403,7 @@ private <T extends Command> void handleByStrategy(final T command,
     }
 
     @Override
-    public void onMutation(final Command command, final E event, final WithDittoHeaders response,
+    public void onMutation(final Command<?> command, final E event, final WithDittoHeaders<?> response,
             final boolean becomeCreated, final boolean becomeDeleted) {
 
         persistAndApplyEvent(event, (persistedEvent, resultingEntity) -> {
@@ -426,14 +427,14 @@ private boolean shouldSendResponse(final DittoHeaders dittoHeaders) {
     }
 
     @Override
-    public void onQuery(final Command command, final WithDittoHeaders response) {
+    public void onQuery(final Command<?> command, final WithDittoHeaders<?> response) {
         if (command.getDittoHeaders().isResponseRequired()) {
             notifySender(response);
         }
     }
 
     @Override
-    public void onError(final DittoRuntimeException error, final Command errorCausingCommand) {
+    public void onError(final DittoRuntimeException error, final Command<?> errorCausingCommand) {
         if (shouldSendResponse(errorCausingCommand.getDittoHeaders())) {
             notifySender(error);
         }
@@ -491,11 +492,11 @@ private void applyEvent(final E event) {
         publishEvent(event);
     }
 
-    private void notifySender(final WithDittoHeaders message) {
+    private void notifySender(final WithDittoHeaders<?> message) {
         notifySender(getSender(), message);
     }
 
-    private void notifySender(final ActorRef sender, final WithDittoHeaders message) {
+    private void notifySender(final ActorRef sender, final WithDittoHeaders<?> message) {
         accessCounter++;
         sender.tell(message, getSelf());
     }
@@ -524,9 +525,9 @@ protected long getLatestSnapshotSequenceNumber() {
     }
 
     private void notAccessible(final Object message) {
-        final DittoRuntimeExceptionBuilder builder = newNotAccessibleExceptionBuilder();
+        final DittoRuntimeExceptionBuilder<?> builder = newNotAccessibleExceptionBuilder();
         if (message instanceof WithDittoHeaders) {
-            builder.dittoHeaders(((WithDittoHeaders) message).getDittoHeaders());
+            builder.dittoHeaders(((WithDittoHeaders<?>) message).getDittoHeaders());
         }
         notifySender(builder.build());
     }
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/commands/AbstractCommandStrategies.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/commands/AbstractCommandStrategies.java
index c186916046..1049b02cca 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/commands/AbstractCommandStrategies.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/commands/AbstractCommandStrategies.java
@@ -32,7 +32,7 @@
  * @param <R> the type of the results
  */
 @Immutable
-public abstract class AbstractCommandStrategies<C extends Command, S, K, R extends Result>
+public abstract class AbstractCommandStrategies<C extends Command<?>, S, K, R extends Result<?>>
         extends AbstractCommandStrategy<C, S, K, R> {
 
     protected final Map<Class<? extends C>, CommandStrategy<? extends C, S, K, R>> strategies;
@@ -43,8 +43,9 @@ public abstract class AbstractCommandStrategies<C extends Command, S, K, R exten
      * @param theMatchingClass the class
      * @throws NullPointerException if {@code theMatchingClass} is {@code null}.
      */
-    protected AbstractCommandStrategies(final Class<C> theMatchingClass) {
-        super(theMatchingClass);
+    @SuppressWarnings({"unchecked", "rawtypes"})
+    protected AbstractCommandStrategies(final Class theMatchingClass) {
+        super((Class<C>) theMatchingClass);
         strategies = new HashMap<>();
     }
 
@@ -102,7 +103,8 @@ protected R doApply(final Context<K> context, @Nullable final S entity, final lo
     }
 
     @Nullable
-    private CommandStrategy<C, S, K, R> getAppropriateStrategy(final Class commandClass) {
+    @SuppressWarnings("unchecked")
+    private CommandStrategy<C, S, K, R> getAppropriateStrategy(final Class<?> commandClass) {
         return (CommandStrategy<C, S, K, R>) strategies.get(commandClass);
     }
 
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/commands/AbstractCommandStrategy.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/commands/AbstractCommandStrategy.java
index 4be9340e91..d0a4c34c6e 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/commands/AbstractCommandStrategy.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/commands/AbstractCommandStrategy.java
@@ -35,7 +35,7 @@
  * @param <R> the type of the result
  */
 @Immutable
-public abstract class AbstractCommandStrategy<C extends Command, S, K, R extends Result>
+public abstract class AbstractCommandStrategy<C extends Command<?>, S, K, R extends Result<?>>
         implements CommandStrategy<C, S, K, R> {
 
     private final Class<C> matchingClass;
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/commands/CommandStrategy.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/commands/CommandStrategy.java
index 447742553f..a207799187 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/commands/CommandStrategy.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/commands/CommandStrategy.java
@@ -26,7 +26,7 @@
  * @param <K> the type of the context
  * @param <R> the type of the results
  */
-public interface CommandStrategy<C extends Command, S, K, R extends Result> {
+public interface CommandStrategy<C extends Command<?>, S, K, R extends Result<?>> {
 
     /**
      * @return the message class to react to.
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/etags/AbstractConditionHeaderCheckingCommandStrategy.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/etags/AbstractConditionHeaderCheckingCommandStrategy.java
index a9e1d259e8..4ccdec5d13 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/etags/AbstractConditionHeaderCheckingCommandStrategy.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/etags/AbstractConditionHeaderCheckingCommandStrategy.java
@@ -40,10 +40,10 @@
  */
 @Immutable
 public abstract class AbstractConditionHeaderCheckingCommandStrategy<
-        C extends Command,
-        S extends Entity,
+        C extends Command<?>,
+        S extends Entity<?>,
         K,
-        E extends Event> extends AbstractCommandStrategy<C, S, K, Result<E>> implements ETagEntityProvider<C, S> {
+        E extends Event<?>> extends AbstractCommandStrategy<C, S, K, Result<E>> implements ETagEntityProvider<C, S> {
 
     /**
      * Construct a command-strategy with condition header checking..
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/events/AbstractEventStrategies.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/events/AbstractEventStrategies.java
index 2710a715d8..67ec24dc77 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/events/AbstractEventStrategies.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/events/AbstractEventStrategies.java
@@ -31,7 +31,7 @@
  * @param <S> the type of the entity
  */
 @Immutable
-public abstract class AbstractEventStrategies<E extends Event, S> implements EventStrategy<E, S> {
+public abstract class AbstractEventStrategies<E extends Event<?>, S> implements EventStrategy<E, S> {
 
     protected final Logger log = LoggerFactory.getLogger(getClass());
 
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/events/EventStrategy.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/events/EventStrategy.java
index b8eac08f59..f2f1c03f7b 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/events/EventStrategy.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/events/EventStrategy.java
@@ -23,7 +23,7 @@
  * @param <S> the type of the entity
  */
 @FunctionalInterface
-public interface EventStrategy<E extends Event, S> {
+public interface EventStrategy<E extends Event<?>, S> {
 
     /**
      * Applies an event to an entity.
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/EmptyResult.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/EmptyResult.java
index dd48c1cf85..964c91f1da 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/EmptyResult.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/EmptyResult.java
@@ -19,9 +19,9 @@
  *
  * @param <E> type of events.
  */
-public final class EmptyResult<E extends Event> implements Result<E> {
+public final class EmptyResult<E extends Event<?>> implements Result<E> {
 
-    private static final Object INSTANCE = new EmptyResult();
+    private static final Object INSTANCE = new EmptyResult<>();
 
     /**
      * Returns the singleton instance of an empty {@link Result}.
@@ -30,12 +30,12 @@ public final class EmptyResult<E extends Event> implements Result<E> {
      * @return the empty result instance.
      */
     @SuppressWarnings("unchecked")
-    public static <E extends Event> EmptyResult<E> getInstance() {
+    public static <E extends Event<?>> EmptyResult<E> getInstance() {
         return (EmptyResult<E>) INSTANCE;
     }
 
     @Override
-    public void accept(final ResultVisitor visitor) {
+    public void accept(final ResultVisitor<E> visitor) {
         visitor.onEmpty();
     }
 
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/ErrorResult.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/ErrorResult.java
index c98904e144..871b648615 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/ErrorResult.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/ErrorResult.java
@@ -19,12 +19,12 @@
 /**
  * Result signifying an error.
  */
-public final class ErrorResult<E extends Event> implements Result<E> {
+public final class ErrorResult<E extends Event<?>> implements Result<E> {
 
-    private final Command errorCausingCommand;
+    private final Command<?> errorCausingCommand;
     private final DittoRuntimeException dittoRuntimeException;
 
-    ErrorResult(final DittoRuntimeException dittoRuntimeException, final Command errorCausingCommand) {
+    ErrorResult(final DittoRuntimeException dittoRuntimeException, final Command<?> errorCausingCommand) {
         this.dittoRuntimeException = dittoRuntimeException;
         this.errorCausingCommand = errorCausingCommand;
     }
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/MutationResult.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/MutationResult.java
index cc7d774c31..b6cbc80e7c 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/MutationResult.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/MutationResult.java
@@ -21,15 +21,15 @@
  *
  * @param <E> type of the event.
  */
-public final class MutationResult<E extends Event> implements Result<E> {
+public final class MutationResult<E extends Event<?>> implements Result<E> {
 
-    private final Command command;
+    private final Command<?> command;
     private final E eventToPersist;
-    private final WithDittoHeaders response;
+    private final WithDittoHeaders<?> response;
     private final boolean becomeCreated;
     private final boolean becomeDeleted;
 
-    MutationResult(final Command command, final E eventToPersist, final WithDittoHeaders response,
+    MutationResult(final Command<?> command, final E eventToPersist, final WithDittoHeaders<?> response,
             final boolean becomeCreated, final boolean becomeDeleted) {
         this.command = command;
         this.eventToPersist = eventToPersist;
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/QueryResult.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/QueryResult.java
index 5b16e64585..ae5e479ab0 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/QueryResult.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/QueryResult.java
@@ -21,12 +21,12 @@
  *
  * @param <E> type of events (irrelevant).
  */
-public final class QueryResult<E extends Event> implements Result<E> {
+public final class QueryResult<E extends Event<?>> implements Result<E> {
 
-    private final Command command;
-    private final WithDittoHeaders response;
+    private final Command<?> command;
+    private final WithDittoHeaders<?> response;
 
-    QueryResult(final Command command, final WithDittoHeaders response) {
+    QueryResult(final Command<?> command, final WithDittoHeaders<?> response) {
         this.command = command;
         this.response = response;
     }
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/Result.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/Result.java
index b93c8aaab6..d05d5d16cb 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/Result.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/Result.java
@@ -17,7 +17,7 @@
 /**
  * The result of applying the strategy to the given command.
  */
-public interface Result<E extends Event> {
+public interface Result<E extends Event<?>> {
 
     /**
      * Evaluate the result by a visitor.
@@ -29,7 +29,7 @@ public interface Result<E extends Event> {
     /**
      * @return the empty result
      */
-    static Result empty() {
+    static <E extends Event<?>> Result<E> empty() {
         return ResultFactory.emptyResult();
     }
 
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/ResultFactory.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/ResultFactory.java
index 7af13f7600..1886a6673c 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/ResultFactory.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/ResultFactory.java
@@ -38,8 +38,8 @@ private ResultFactory() {
      * @param <E> type of the event.
      * @return the result.
      */
-    public static <E extends Event> Result<E> newMutationResult(final Command command, final E eventToPersist,
-            final WithDittoHeaders response) {
+    public static <E extends Event<?>> Result<E> newMutationResult(final Command<?> command, final E eventToPersist,
+            final WithDittoHeaders<?> response) {
 
         return new MutationResult<>(command, eventToPersist, response, false, false);
     }
@@ -55,9 +55,9 @@ public static <E extends Event> Result<E> newMutationResult(final Command comman
      * @param <E> type of the event.
      * @return the result.
      */
-    public static <E extends Event> Result<E> newMutationResult(final Command command,
+    public static <E extends Event<?>> Result<E> newMutationResult(final Command<?> command,
             final E eventToPersist,
-            final WithDittoHeaders response,
+            final WithDittoHeaders<?> response,
             final boolean becomeCreated,
             final boolean becomeDeleted) {
 
@@ -72,8 +72,8 @@ public static <E extends Event> Result<E> newMutationResult(final Command comman
      * @param <E> type of events (irrelevant).
      * @return the result.
      */
-    public static <E extends Event> Result<E> newErrorResult(final DittoRuntimeException dittoRuntimeException,
-            final Command errorCausingCommand) {
+    public static <E extends Event<?>> Result<E> newErrorResult(final DittoRuntimeException dittoRuntimeException,
+            final Command<?> errorCausingCommand) {
         return new ErrorResult<>(dittoRuntimeException, errorCausingCommand);
     }
 
@@ -85,7 +85,8 @@ public static <E extends Event> Result<E> newErrorResult(final DittoRuntimeExcep
      * @param <E> type of events (irrelevant).
      * @return the result.
      */
-    public static <E extends Event> Result<E> newQueryResult(final Command command, final WithDittoHeaders response) {
+    public static <E extends Event<?>> Result<E> newQueryResult(final Command<?> command,
+            final WithDittoHeaders<?> response) {
         return new QueryResult<>(command, response);
     }
 
@@ -95,7 +96,7 @@ public static <E extends Event> Result<E> newQueryResult(final Command command,
      * @param <E> type of events (irrelevant).
      * @return the empty result.
      */
-    public static <E extends Event> Result<E> emptyResult() {
+    public static <E extends Event<?>> Result<E> emptyResult() {
         return EmptyResult.getInstance();
     }
 
diff --git a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/ResultVisitor.java b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/ResultVisitor.java
index e1aad85e75..b9efd6034c 100644
--- a/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/ResultVisitor.java
+++ b/services/utils/persistent-actors/src/main/java/org/eclipse/ditto/services/utils/persistentactors/results/ResultVisitor.java
@@ -22,7 +22,7 @@
  *
  * @param <E> type of events.
  */
-public interface ResultVisitor<E extends Event> {
+public interface ResultVisitor<E extends Event<?>> {
 
     /**
      * Evaluate the empty result. Do nothing by default.
@@ -40,7 +40,7 @@ default void onEmpty() {
      * @param becomeCreated whether the actor should behave as if the entity is created.
      * @param becomeDeleted whether the actor should behave as if the entity is deleted.
      */
-    void onMutation(Command command, E event, WithDittoHeaders response, boolean becomeCreated, boolean becomeDeleted);
+    void onMutation(Command<?> command, E event, WithDittoHeaders<?> response, boolean becomeCreated, boolean becomeDeleted);
 
     /**
      * Evaluate a query result.
@@ -48,12 +48,12 @@ default void onEmpty() {
      * @param command the query command.
      * @param response the response.
      */
-    void onQuery(Command command, WithDittoHeaders response);
+    void onQuery(Command<?> command, WithDittoHeaders<?> response);
 
     /**
      * Evaluate an error result.
      *
      * @param error the error.
      */
-    void onError(DittoRuntimeException error, Command errorCausingCommand);
+    void onError(DittoRuntimeException error, Command<?> errorCausingCommand);
 }