diff --git a/pom.xml b/pom.xml
index 2d19925..d9f3692 100644
--- a/pom.xml
+++ b/pom.xml
@@ -16,8 +16,8 @@
     <url>http://s3ninja.net</url>
 
     <properties>
-        <sirius.kernel>dev-31.1.0</sirius.kernel>
-        <sirius.web>dev-52.1.1</sirius.web>
+        <sirius.kernel>dev-33.1.0</sirius.kernel>
+        <sirius.web>dev-57.3.0</sirius.web>
     </properties>
 
     <repositories>
@@ -55,7 +55,7 @@
         <dependency>
             <groupId>com.amazonaws</groupId>
             <artifactId>aws-java-sdk-s3</artifactId>
-            <version>1.12.261</version>
+            <version>1.12.307</version>
         </dependency>
     </dependencies>
 </project>
diff --git a/src/main/java/ninja/Bucket.java b/src/main/java/ninja/Bucket.java
index 961eaf8..249f741 100644
--- a/src/main/java/ninja/Bucket.java
+++ b/src/main/java/ninja/Bucket.java
@@ -307,7 +307,7 @@ public List<StoredObject> getObjects(@Nullable String query, Limit limit) {
                          .filter(currentFile -> isMatchingObject(query, currentFile))
                          .filter(limit.asPredicate())
                          .map(StoredObject::new)
-                         .collect(Collectors.toList());
+                         .toList();
         } catch (IOException e) {
             throw Exceptions.handle(e);
         }
diff --git a/src/main/java/ninja/S3Dispatcher.java b/src/main/java/ninja/S3Dispatcher.java
index 16dec33..e0f5625 100644
--- a/src/main/java/ninja/S3Dispatcher.java
+++ b/src/main/java/ninja/S3Dispatcher.java
@@ -137,16 +137,6 @@ private static class S3Request {
                                           .withChronology(IsoChronology.INSTANCE)
                                           .withZone(ZoneOffset.ofHours(0));
 
-    /**
-     * RFC 822 date/time formatter.
-     */
-    public static final DateTimeFormatter RFC822_INSTANT =
-            new DateTimeFormatterBuilder().appendPattern("EEE, dd MMM yyyy HH:mm:ss 'GMT'")
-                                          .toFormatter()
-                                          .withLocale(Locale.ENGLISH)
-                                          .withChronology(IsoChronology.INSTANCE)
-                                          .withZone(ZoneOffset.ofHours(0));
-
     private static final Map<String, String> headerOverrides;
 
     static {
@@ -658,10 +648,10 @@ private void deleteObject(final WebContext webContext, final Bucket bucket, fina
                 object.markDeleted();
             } catch (IOException ignored) {
                 signalObjectError(webContext,
-                        bucket.getName(),
-                        id,
-                        S3ErrorCode.InternalError,
-                        Strings.apply("Error while marking file as deleted"));
+                                  bucket.getName(),
+                                  id,
+                                  S3ErrorCode.InternalError,
+                                  Strings.apply("Error while marking file as deleted"));
                 return;
             }
         }
@@ -794,7 +784,8 @@ private void getObject(WebContext webContext, Bucket bucket, String id, boolean
         StoredObject object = bucket.getObject(id);
         if (!object.exists() && !object.isMarkedDeleted() && awsUpstream.isConfigured()) {
             URL fetchURL = awsUpstream.generateGetObjectURL(bucket, object, sendFile);
-            Consumer<BoundRequestBuilder> requestTuner = requestBuilder -> requestBuilder.setMethod(sendFile ? "GET" : "HEAD");
+            Consumer<BoundRequestBuilder> requestTuner =
+                    requestBuilder -> requestBuilder.setMethod(sendFile ? "GET" : "HEAD");
             webContext.enableTiming(null).respondWith().tunnel(fetchURL.toString(), requestTuner, null, null);
             return;
         }
@@ -829,7 +820,7 @@ private void getObject(WebContext webContext, Bucket bucket, String id, boolean
             String contentType = MimeHelper.guessMimeType(object.getFile().getName());
             response.addHeader(HttpHeaderNames.CONTENT_TYPE, contentType);
             response.addHeader(HttpHeaderNames.LAST_MODIFIED,
-                               RFC822_INSTANT.format(Instant.ofEpochMilli(object.getFile().lastModified())));
+                               Response.RFC822_INSTANT.format(Instant.ofEpochMilli(object.getFile().lastModified())));
             response.addHeader(HttpHeaderNames.CONTENT_LENGTH, object.getFile().length());
             response.status(HttpResponseStatus.OK);
         }
@@ -967,7 +958,7 @@ private void completeMultipartUpload(WebContext webContext,
                                       .stream()
                                       .sorted(Comparator.comparing(Map.Entry::getKey))
                                       .map(Map.Entry::getValue)
-                                      .collect(Collectors.toList()));
+                                      .toList());
 
         file.deleteOnExit();
         if (!file.exists()) {
diff --git a/src/main/resources/application.conf b/src/main/resources/application.conf
index 4ac65c7..7d35c34 100644
--- a/src/main/resources/application.conf
+++ b/src/main/resources/application.conf
@@ -42,6 +42,25 @@ storage {
   awsSecretKey = "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY"
 }
 
+# Configures an upstream S3 instance which can be used in case an object is not found locally.
+upstreamAWS {
+    # The secret key to connect to the upstream S3 instance.
+    secretKey = ""
+
+    # The access key to connect to the upstream S3 instance.
+    accessKey = ""
+    # The endpoint used to connect to the upstream S3 instance.
+    endPoint = ""
+
+    # The signing region used to connect to the upstream S3 instance.
+    # If not given, the value "EU" is used.
+    signingRegion = ""
+
+    # The signer type used to connect to the upstream S3 instance.
+    # This config is optional and will be ignored if missing.
+    signerType = ""
+}
+
 cache {
     public-bucket-access {
         maxSize = 128