diff --git a/plutus-pab-executables/plutus-pab.yaml.sample b/plutus-pab-executables/plutus-pab.yaml.sample
index 227ee316d0..bab824ec71 100644
--- a/plutus-pab-executables/plutus-pab.yaml.sample
+++ b/plutus-pab-executables/plutus-pab.yaml.sample
@@ -10,6 +10,7 @@ pabWebserverConfig:
   # available. If this is not set, calls to unavailable endpoints fail
   # immediately.
   endpointTimeout: 5
+  enableMarconi: False
 
 walletServerConfig:
   tag: LocalWalletConfig
diff --git a/plutus-pab/src/Plutus/PAB/Core/ContractInstance/BlockchainEnv.hs b/plutus-pab/src/Plutus/PAB/Core/ContractInstance/BlockchainEnv.hs
index 40b7bb39c8..ba91b231f0 100644
--- a/plutus-pab/src/Plutus/PAB/Core/ContractInstance/BlockchainEnv.hs
+++ b/plutus-pab/src/Plutus/PAB/Core/ContractInstance/BlockchainEnv.hs
@@ -17,6 +17,7 @@ import Cardano.Protocol.Socket.Client (ChainSyncEvent (..))
 import Cardano.Protocol.Socket.Client qualified as Client
 import Cardano.Protocol.Socket.Mock.Client qualified as MockClient
 import Control.Lens.Operators
+import Control.Monad (when)
 import Data.Either (isLeft)
 import Data.IORef (newIORef, readIORef, writeIORef)
 import Data.List (findIndex)
@@ -27,23 +28,25 @@ import Data.Text (unpack)
 import Ledger (Block, Slot (..), TxId (..))
 import Marconi.Index.TxConfirmationStatus (TxInfo (..))
 import Marconi.Index.TxConfirmationStatus qualified as Ix
+import Plutus.ChainIndex.TxIdState qualified as TxIdState
 import Plutus.HystericalScreams.Index.VSqlite qualified as Ix
 import Plutus.PAB.Core.ContractInstance.STM (BlockchainEnv (..), InstanceClientEnv (..), InstancesState,
                                              OpenTxOutProducedRequest (..), OpenTxOutSpentRequest (..),
-                                             emptyBlockchainEnv, getIndexerTxChanges, getUtxoIndexTxChanges)
+                                             emptyBlockchainEnv, getUtxoIndexTxChanges)
 import Plutus.PAB.Core.ContractInstance.STM qualified as S
 import Plutus.Trace.Emulator.ContractInstance (IndexedBlock (..), indexBlock)
 
 import Plutus.PAB.Types (Config (Config), DbConfig (DbConfig, dbConfigFile),
-                         DevelopmentOptions (DevelopmentOptions, pabResumeFrom, pabRollbackHistory), dbConfig,
-                         developmentOptions, nodeServerConfig)
+                         DevelopmentOptions (DevelopmentOptions, pabResumeFrom, pabRollbackHistory),
+                         WebserverConfig (WebserverConfig, enableMarconi), dbConfig, developmentOptions,
+                         nodeServerConfig, pabWebserverConfig)
 
 import Cardano.Node.Types (NodeMode (..),
                            PABServerConfig (PABServerConfig, pscNetworkId, pscNodeMode, pscSlotConfig, pscSocketPath))
 import Control.Concurrent.STM (STM)
 import Control.Concurrent.STM qualified as STM
 import Control.Lens
-import Control.Monad (forM_, void, when)
+import Control.Monad (forM_, void)
 import Control.Tracer (nullTracer)
 import Data.Foldable (foldl')
 import Data.Maybe (catMaybes, maybeToList)
@@ -77,6 +80,8 @@ startNodeClient config instancesState = do
                                       , pabResumeFrom = resumePoint
                                       }
                , dbConfig = DbConfig { dbConfigFile = dbFile }
+               , pabWebserverConfig =
+                   WebserverConfig { enableMarconi = useMarconiIndexer }
                } = config
     params <- Params.fromPABServerConfig $ nodeServerConfig config
     env <- STM.atomically $ emptyBlockchainEnv pabRollbackHistory params
@@ -86,8 +91,13 @@ startNodeClient config instancesState = do
             (\block slot -> handleSyncAction $ processMockBlock instancesState env block slot
             )
       AlonzoNode -> do
-        utxoIx <- Ix.open (unpack dbFile) (Ix.Depth 2160) >>= newIORef
-        let env' = env { beTxChanges = Right utxoIx }
+        env' <-
+          if useMarconiIndexer
+          then do
+            utxoIx <- Ix.open (unpack dbFile) (Ix.Depth 2160) >>= newIORef
+            pure $ env { beTxChanges = Right utxoIx }
+          else do
+            pure env
         let resumePoints = maybeToList $ toCardanoPoint resumePoint
         void $ Client.runChainSync socket nullTracer slotConfig networkId resumePoints
             (\block -> do
@@ -137,23 +147,26 @@ processChainSyncEvent
   -> BlockchainEnv
   -> ChainSyncEvent
   -> IO (Either SyncActionFailure (Slot, BlockNumber))
-processChainSyncEvent instancesState blockchainEnv event = do
+processChainSyncEvent instancesState env@BlockchainEnv{beTxChanges} event = do
   case event of
-    Resume _ -> STM.atomically $ Right <$> blockAndSlot blockchainEnv
+    Resume _ -> STM.atomically $ Right <$> blockAndSlot env
     RollForward (BlockInMode (C.Block header transactions) era) _ ->
-      withIsCardanoEra era (processBlock instancesState header blockchainEnv transactions era)
+      withIsCardanoEra era (processBlock instancesState header env transactions era)
     RollBackward chainPoint _ -> do
-      -- Rollback the index
-      ix'    <- readIORef $ getIndexerTxChanges blockchainEnv
-      events <- concat <$> Ix.getEvents (ix' ^. Ix.storage)
-      -- TODO: Stop ignoring errors.
-      let nextIx = fromMaybe ix' $ do
-                     slot   <- chainPointToSlotNo chainPoint
-                     offset <- findIndex (\(TxInfo _ _ sn) -> sn < slot) events
-                     Ix.rewind offset ix'
-      writeIORef (getIndexerTxChanges blockchainEnv) nextIx
-
-      STM.atomically $ runRollback blockchainEnv chainPoint
+      either (const $ pure ())
+             (\ixRef -> do
+                 -- Rollback the index
+                 ix'    <- readIORef ixRef
+                 events <- concat <$> Ix.getEvents (ix' ^. Ix.storage)
+                 -- TODO: Stop ignoring errors.
+                 let nextIx = fromMaybe ix' $ do
+                                slot   <- chainPointToSlotNo chainPoint
+                                offset <- findIndex (\(TxInfo _ _ sn) -> sn < slot) events
+                                Ix.rewind offset ix'
+                 writeIORef ixRef nextIx)
+              beTxChanges
+
+      STM.atomically $ runRollback env chainPoint
 
 data SyncActionFailure
   = RollbackFailure RollbackFailed
@@ -162,24 +175,38 @@ data SyncActionFailure
 
 -- | Roll back the chain to the given ChainPoint and slot.
 runRollback :: BlockchainEnv -> ChainPoint -> STM (Either SyncActionFailure (Slot, BlockNumber))
-runRollback env@BlockchainEnv{beLastSyncedBlockSlot, beTxOutChanges} chainPoint = do
+runRollback env@BlockchainEnv{beTxChanges, beLastSyncedBlockSlot, beTxOutChanges} chainPoint = do
   currentSlot <- STM.readTVar beLastSyncedBlockSlot
   txOutBalanceStateIndex <- STM.readTVar beTxOutChanges
 
   let point = fromCardanoPoint chainPoint
-      rs   = TxOutBalance.rollback point txOutBalanceStateIndex
+      rs'   = TxOutBalance.rollback point txOutBalanceStateIndex
       -- Check to see if the rollback is just through a sequence of empty blocks ending at the tip.
       emptyRollBack =
            point > tipAsPoint (viewTip txOutBalanceStateIndex)
         && pointSlot point <= currentSlot
 
+  rs <- case beTxChanges of
+          Left ix' -> do
+            txIdStateIndex <- STM.readTVar ix'
+            pure $ TxIdState.rollback point txIdStateIndex
+          Right _  ->
+            pure $ Right RollbackResult { newTip = TipAtGenesis
+                                        , rolledBackIndex = mempty
+                                        }
   if emptyRollBack
     then Right <$> blockAndSlot env
     else case rs of
-           Left e' -> pure $ Left (RollbackFailure e')
-           Right RollbackResult{rolledBackIndex=rolledBackTxOutBalanceStateIndex} -> do
-             STM.writeTVar beTxOutChanges rolledBackTxOutBalanceStateIndex
-             Right <$> blockAndSlot env
+           Left e  -> pure $ Left (RollbackFailure e)
+           Right RollbackResult{rolledBackIndex=rolledBackTxIdStateIndex} -> do
+             case rs' of
+               Left e' -> pure $ Left (RollbackFailure e')
+               Right RollbackResult{rolledBackIndex=rolledBackTxOutBalanceStateIndex} -> do
+                 STM.writeTVar beTxOutChanges rolledBackTxOutBalanceStateIndex
+                 either (\ix' -> STM.writeTVar ix' rolledBackTxIdStateIndex)
+                        (const $ pure ())
+                        beTxChanges
+                 Right <$> blockAndSlot env
 
 -- | Get transaction ID and validity from a transaction.
 txEvent :: ChainIndexTx -> (TxId, TxOutBalance, TxValidity)
@@ -197,7 +224,7 @@ processBlock :: forall era. C.IsCardanoEra era
              -> [C.Tx era]
              -> C.EraInMode era C.CardanoMode
              -> IO (Either SyncActionFailure (Slot, BlockNumber))
-processBlock instancesState header env transactions era = do
+processBlock instancesState header env@BlockchainEnv{beTxChanges} transactions era = do
   let C.BlockHeader (C.SlotNo slot) _ _ = header
       tip = fromCardanoBlockHeader header
       -- We ignore cardano transactions that we couldn't convert to
@@ -213,9 +240,13 @@ processBlock instancesState header env transactions era = do
           updateInstances (indexBlock ciTxs) instEnv
           updateEmulatorTransactionState tip env (txEvent <$> ciTxs)
 
-  ix'    <- readIORef $ getIndexerTxChanges env
-  nextIx <- Ix.insert (mkEvent tip <$> ciTxs) ix'
-  writeIORef (getIndexerTxChanges env) nextIx
+  either (const $ pure ())
+         (\ixRef -> do
+             ix'    <- readIORef ixRef
+             nextIx <- Ix.insert (mkEvent tip <$> ciTxs) ix'
+             writeIORef ixRef nextIx)
+         beTxChanges
+
   pure stmResult
 
 mkEvent :: Tip -> ChainIndexTx -> TxInfo
diff --git a/plutus-pab/src/Plutus/PAB/Core/ContractInstance/STM.hs b/plutus-pab/src/Plutus/PAB/Core/ContractInstance/STM.hs
index 1e123bae25..e1ffd4f7fe 100644
--- a/plutus-pab/src/Plutus/PAB/Core/ContractInstance/STM.hs
+++ b/plutus-pab/src/Plutus/PAB/Core/ContractInstance/STM.hs
@@ -18,7 +18,6 @@ module Plutus.PAB.Core.ContractInstance.STM(
     , currentSlot
     , lastSyncedBlockSlot
     , getUtxoIndexTxChanges
-    , getIndexerTxChanges
     -- * State of a contract instance
     , InstanceState(..)
     , emptyInstanceState
@@ -57,7 +56,7 @@ import Control.Concurrent.STM (STM, TMVar, TVar)
 import Control.Concurrent.STM qualified as STM
 import Control.Monad (guard, (<=<))
 import Data.Aeson (Value)
-import Data.Either (fromLeft, fromRight)
+import Data.Either (fromLeft)
 import Data.Foldable (fold)
 import Data.IORef (IORef)
 import Data.List.NonEmpty (NonEmpty)
@@ -167,10 +166,6 @@ getUtxoIndexTxChanges :: BlockchainEnv -> TVar (UtxoIndex TxIdState)
 getUtxoIndexTxChanges BlockchainEnv{beTxChanges} =
     fromLeft (error "Changes use an indexer for storage.") beTxChanges
 
-getIndexerTxChanges :: BlockchainEnv -> IORef TCSIndex
-getIndexerTxChanges BlockchainEnv{beTxChanges} =
-    fromRight (error "Changes use in-memory storage, not an indexer.") beTxChanges
-
 -- | Initialise an empty 'BlockchainEnv' value
 emptyBlockchainEnv :: Maybe Int -> Params -> STM BlockchainEnv
 emptyBlockchainEnv rollbackHistory params =
diff --git a/plutus-pab/src/Plutus/PAB/Types.hs b/plutus-pab/src/Plutus/PAB/Types.hs
index 4fdb0903ba..cc232f9b19 100644
--- a/plutus-pab/src/Plutus/PAB/Types.hs
+++ b/plutus-pab/src/Plutus/PAB/Types.hs
@@ -162,6 +162,7 @@ data WebserverConfig =
         , staticDir            :: Maybe FilePath
         , permissiveCorsPolicy :: Bool -- ^ If true; use a very permissive CORS policy (any website can interact.)
         , endpointTimeout      :: Maybe Second
+        , enableMarconi        :: Bool
         }
     deriving (Show, Eq, Generic)
     deriving anyclass (FromJSON, ToJSON)
@@ -175,6 +176,7 @@ defaultWebServerConfig =
     , staticDir            = Nothing
     , permissiveCorsPolicy = False
     , endpointTimeout      = Nothing
+    , enableMarconi        = False
     }
 
 instance Default WebserverConfig where