diff --git a/config/settings.yml b/config/settings.yml
index ea6d0dd97..024a72945 100644
--- a/config/settings.yml
+++ b/config/settings.yml
@@ -157,6 +157,10 @@ memcached:
   limit:      "_env:MEMCACHED_LIMIT:1024"
   timeout:    "_env:MEMCACHED_TIMEOUT:20"
   expiration: "_env:MEMCACHED_EXPIRATION:300"
+memcache-auth: true
+memcached-local:
+  maximum-ghost: 512
+  maximum-weight: 104857600 # 100MiB
 
 upload-cache:
   host: "_env:UPLOAD_S3_HOST:"
@@ -269,8 +273,6 @@ fallback-personalised-sheet-files-keys-expire: 2419200
 
 download-token-expire: 604801
 
-memcache-auth: true
-
 file-source-arc:
   maximum-ghost: 512
   maximum-weight: 1073741824 # 1GiB
diff --git a/src/Application.hs b/src/Application.hs
index a14c41403..bcaf1edda 100644
--- a/src/Application.hs
+++ b/src/Application.hs
@@ -112,6 +112,9 @@ import qualified Data.IntervalMap.Strict as IntervalMap
 
 import qualified Utils.Pool as Custom
 
+import Utils.Postgresql
+import Handler.Utils.Memcached (manageMemcachedLocalInvalidations)
+
 -- Import all relevant handler modules here.
 -- (HPack takes care to add new modules to our cabal file nowadays.)
 import Handler.News
@@ -208,7 +211,7 @@ makeFoundation appSettings''@AppSettings{..} = do
     -- from there, and then create the real foundation.
     let
       mkFoundation :: _ -> (forall m. MonadIO m => Custom.Pool' m DBConnLabel DBConnUseState SqlBackend) -> _
-      mkFoundation appSettings' appConnPool appSmtpPool appLdapPool appCryptoIDKey appSessionStore appSecretBoxKey appWidgetMemcached appJSONWebKeySet appClusterID appMemcached appUploadCache appVerpSecret appAuthKey = UniWorX {..}
+      mkFoundation appSettings' appConnPool appSmtpPool appLdapPool appCryptoIDKey appSessionStore appSecretBoxKey appWidgetMemcached appJSONWebKeySet appClusterID appMemcached appMemcachedLocal appUploadCache appVerpSecret appAuthKey = UniWorX {..}
       -- The UniWorX {..} syntax is an example of record wild cards. For more
       -- information, see:
       -- https://ocharles.org.uk/blog/posts/2014-12-04-record-wildcards.html
@@ -224,6 +227,7 @@ makeFoundation appSettings''@AppSettings{..} = do
         (error "JSONWebKeySet forced in tempFoundation")
         (error "ClusterID forced in tempFoundation")
         (error "memcached forced in tempFoundation")
+        (error "memcachedLocal forced in tempFoundation")
         (error "MinioConn forced in tempFoundation")
         (error "VerpSecret forced in tempFoundation")
         (error "AuthKey forced in tempFoundation")
@@ -295,11 +299,17 @@ makeFoundation appSettings''@AppSettings{..} = do
       appMemcached <- for appMemcachedConf $ \memcachedConf -> do
         $logDebugS "setup" "Memcached"
         memcachedKey <- clusterSetting (Proxy :: Proxy 'ClusterMemcachedKey) `customRunSqlPool` sqlPool
-        memcached <- createMemcached memcachedConf
+        memcachedConn <- createMemcached memcachedConf
         when appClearCache $ do
           $logWarnS "setup" "Clearing memcached"
-          liftIO $ Memcached.flushAll memcached
-        return (memcachedKey, memcached)
+          liftIO $ Memcached.flushAll memcachedConn
+        return AppMemcached{..}
+      appMemcachedLocal <- for appMemcachedLocalConf $ \ARCConf{..} -> do
+        memcachedLocalARC <- initARCHandle arccMaximumGhost arccMaximumWeight
+        void . Prometheus.register $ arcMetrics ARCMemcachedLocal memcachedLocalARC
+        memcachedLocalInvalidationQueue <- newTVarIO mempty
+        memcachedLocalHandleInvalidations <- allocateLinkedAsync . managePostgresqlChannel appDatabaseConf ChannelMemcachedLocalInvalidation $ manageMemcachedLocalInvalidations memcachedLocalARC memcachedLocalInvalidationQueue
+        return AppMemcachedLocal{..}
 
       appSessionStore <- mkSessionStore appSettings'' sqlPool `customRunSqlPool` sqlPool
 
@@ -314,7 +324,7 @@ makeFoundation appSettings''@AppSettings{..} = do
 
       $logDebugS "Runtime configuration" $ tshow appSettings'
 
-      let foundation = mkFoundation appSettings' sqlPool smtpPool ldapPool appCryptoIDKey appSessionStore appSecretBoxKey appWidgetMemcached appJSONWebKeySet appClusterID appMemcached appUploadCache appVerpSecret appAuthKey
+      let foundation = mkFoundation appSettings' sqlPool smtpPool ldapPool appCryptoIDKey appSessionStore appSecretBoxKey appWidgetMemcached appJSONWebKeySet appClusterID appMemcached appMemcachedLocal appUploadCache appVerpSecret appAuthKey
 
       -- Return the foundation
       $logDebugS "setup" "Done"
@@ -671,7 +681,7 @@ shutdownApp app = do
     for_ (appSmtpPool app) destroyAllResources
     for_ (appLdapPool app) . mapFailover $ views _2 destroyAllResources
     for_ (appWidgetMemcached app) Memcached.close
-    for_ (appMemcached app) $ views _2 Memcached.close
+    for_ (appMemcached app) $ views _memcachedConn Memcached.close
   release . fst $ appLogger app
 
   liftIO $ threadDelay 1e6
diff --git a/src/Database/Persist/Sql/Types/Instances.hs b/src/Database/Persist/Sql/Types/Instances.hs
index cc7219bc3..4fd50d57a 100644
--- a/src/Database/Persist/Sql/Types/Instances.hs
+++ b/src/Database/Persist/Sql/Types/Instances.hs
@@ -24,3 +24,4 @@ instance BackendCompatible SqlWriteBackend SqlBackend where
   projectBackend = SqlWriteBackend
 
 deriving newtype instance Binary (BackendKey SqlBackend)
+deriving anyclass instance NFData (BackendKey SqlBackend)
diff --git a/src/Foundation/Authorization.hs b/src/Foundation/Authorization.hs
index a318ca559..cd0c34b01 100644
--- a/src/Foundation/Authorization.hs
+++ b/src/Foundation/Authorization.hs
@@ -157,7 +157,7 @@ instance (MonadHandler m, HandlerSite m ~ UniWorX, BackendCompatible SqlReadBack
 -- cacheAP mExp k mkV cont = APBind $ \mAuthId route isWrite -> either (return . Left) (fmap Right) . cont mAuthId route isWrite =<< memcachedBy mExp k mkV
 
 cacheAPDB :: ( Binary k
-             , Typeable v, Binary v
+             , Typeable v, Binary v, NFData v
              )
           => Maybe Expiry
           -> k
@@ -185,7 +185,7 @@ cacheAPDB mExp k mkV cont = APBindDB $ \mAuthId route isWrite -> do
 --   Nothing -> either (return . Left) (fmap Right) $ cont mAuthId route isWrite Nothing
   
 cacheAPDB' :: ( Binary k
-              , Typeable v, Binary v
+              , Typeable v, Binary v, NFData v
               )
            => Maybe Expiry
            -> (Maybe (AuthId UniWorX) -> Route UniWorX -> Bool -> Maybe (k, ReaderT SqlReadBackend (HandlerFor UniWorX) v))
diff --git a/src/Foundation/Type.hs b/src/Foundation/Type.hs
index 6f9fb8091..3b7494d3c 100644
--- a/src/Foundation/Type.hs
+++ b/src/Foundation/Type.hs
@@ -5,6 +5,10 @@ module Foundation.Type
   ( UniWorX(..)
   , SomeSessionStorage(..)
   , _SessionStorageMemcachedSql, _SessionStorageAcid
+  , AppMemcached(..)
+  , _memcachedKey, _memcachedConn
+  , AppMemcachedLocal(..)
+  , _memcachedLocalARC
   , SMTPPool
   , _appSettings', _appStatic, _appConnPool, _appSmtpPool, _appLdapPool, _appWidgetMemcached, _appHttpManager, _appLogger, _appLogSettings, _appCryptoIDKey, _appClusterID, _appInstanceID, _appJobState, _appSessionStore, _appSecretBoxKey, _appJSONWebKeySet, _appHealthReport, _appMemcached, _appUploadCache, _appVerpSecret, _appAuthKey
   , DB, Form, MsgRenderer, MailM, DBFile
@@ -30,15 +34,35 @@ import qualified Utils.Pool as Custom
 
 import Utils.Metrics (DBConnUseState)
 
+import qualified Data.ByteString.Lazy as Lazy
+import Data.Time.Clock.POSIX (POSIXTime)
+import GHC.Fingerprint (Fingerprint)
+
 
 type SMTPPool = Pool SMTPConnection
 
 data SomeSessionStorage
   = SessionStorageMemcachedSql { sessionStorageMemcachedSql :: MemcachedSqlStorage SessionMap }
   | SessionStorageAcid { sessionStorageAcid :: AcidStorage SessionMap }
+  deriving (Generic, Typeable)
 
 makePrisms ''SomeSessionStorage
 
+data AppMemcached = AppMemcached
+  { memcachedKey :: AEAD.Key
+  , memcachedConn :: Memcached.Connection
+  } deriving (Generic, Typeable)
+
+makeLenses_ ''AppMemcached
+
+data AppMemcachedLocal = AppMemcachedLocal
+  { memcachedLocalARC :: ARCHandle (Fingerprint, Lazy.ByteString) Int (NFDynamic, Maybe POSIXTime)
+  , memcachedLocalHandleInvalidations :: Async ()
+  , memcachedLocalInvalidationQueue :: TVar (Seq (Fingerprint, Lazy.ByteString))
+  } deriving (Generic, Typeable)
+
+makeLenses_ ''AppMemcachedLocal
+
 -- | The foundation datatype for your application. This can be a good place to
 -- keep settings and values requiring initialization before your application
 -- starts running, such as database connections. Every handler will have
@@ -61,14 +85,15 @@ data UniWorX = UniWorX
     , appSecretBoxKey      :: SecretBox.Key
     , appJSONWebKeySet     :: Jose.JwkSet
     , appHealthReport      :: TVar (Set (UTCTime, HealthReport))
-    , appMemcached         :: Maybe (AEAD.Key, Memcached.Connection)
+    , appMemcached         :: Maybe AppMemcached
+    , appMemcachedLocal    :: Maybe AppMemcachedLocal
     , appUploadCache       :: Maybe MinioConn
     , appVerpSecret        :: VerpSecret
     , appAuthKey           :: Auth.Key
     , appFileSourceARC     :: Maybe (ARCHandle (FileContentChunkReference, (Int, Int)) Int ByteString)
     , appFileSourcePrewarm :: Maybe (LRUHandle (FileContentChunkReference, (Int, Int)) UTCTime Int ByteString)
     , appFileInjectInhibit :: TVar (IntervalMap UTCTime (Set FileContentReference))
-    }
+    } deriving (Typeable)
 
 makeLenses_ ''UniWorX
 instance HasInstanceID UniWorX InstanceId where
diff --git a/src/Handler/Utils.hs b/src/Handler/Utils.hs
index 12ee98805..76b3496f1 100644
--- a/src/Handler/Utils.hs
+++ b/src/Handler/Utils.hs
@@ -22,7 +22,7 @@ import Handler.Utils.I18n       as Handler.Utils
 import Handler.Utils.Widgets    as Handler.Utils
 import Handler.Utils.Database   as Handler.Utils
 import Handler.Utils.Occurrences as Handler.Utils
-import Handler.Utils.Memcached  as Handler.Utils
+import Handler.Utils.Memcached  as Handler.Utils hiding (manageMemcachedLocalInvalidations)
 import Handler.Utils.Files      as Handler.Utils
 import Handler.Utils.Download   as Handler.Utils
 
diff --git a/src/Handler/Utils/Memcached.hs b/src/Handler/Utils/Memcached.hs
index 58a081b36..de06f6103 100644
--- a/src/Handler/Utils/Memcached.hs
+++ b/src/Handler/Utils/Memcached.hs
@@ -1,9 +1,12 @@
+{-# LANGUAGE DuplicateRecordFields #-}
+
 module Handler.Utils.Memcached
   ( memcachedAvailable
   , memcached, memcachedBy
   , memcachedHere, memcachedByHere
   , memcachedSet, memcachedGet
   , memcachedInvalidate, memcachedByInvalidate
+  , manageMemcachedLocalInvalidations
   , memcachedByGet, memcachedBySet
   , memcachedTimeout, memcachedTimeoutBy
   , memcachedTimeoutHere, memcachedTimeoutByHere
@@ -35,9 +38,11 @@ import Crypto.Hash.Algorithms (SHAKE256)
 
 import qualified Data.ByteArray as BA
 
+import qualified Data.ByteString.Base64 as Base64
+
 import Language.Haskell.TH hiding (Type)
 
-import Data.Typeable (typeRep)
+import Data.Typeable (typeRep, typeRepFingerprint)
 import Type.Reflection (typeOf, TypeRep)
 import qualified Type.Reflection as Refl (typeRep)
 import Data.Type.Equality (TestEquality(..))
@@ -58,6 +63,12 @@ import qualified Control.Monad.State.Class as State
 
 import qualified Data.ByteString.Lazy as Lazy (ByteString)
 
+import GHC.Fingerprint
+
+import Utils.Postgresql
+
+import UnliftIO.Concurrent (threadDelay)
+
 
 type Expiry = Either UTCTime DiffTime
 
@@ -112,7 +123,7 @@ putMemcachedValue MemcachedValue{..} = do
   putExpiry mExpiry
   Binary.putByteString mCiphertext
 
-getMemcachedValue :: Binary.Get MemcachedValue
+getMemcachedValue, getMemcachedValueNoExpiry :: Binary.Get MemcachedValue
 getMemcachedValue = do
   Binary.lookAhead . Binary.label "length check" $ do
     void . Binary.getByteString $ Saltine.secretBoxNonce + 4 + Saltine.secretBoxMac
@@ -120,8 +131,6 @@ getMemcachedValue = do
   mExpiry <- getExpiry
   mCiphertext <- Binary.label "ciphertext" $ toStrict <$> Binary.getRemainingLazyByteString
   return MemcachedValue{..}
-
-getMemcachedValueNoExpiry :: Binary.Get MemcachedValue
 getMemcachedValueNoExpiry = do
   Binary.lookAhead . Binary.label "length check" $ do
     void . Binary.getByteString $ Saltine.secretBoxNonce + 4 + Saltine.secretBoxMac
@@ -130,7 +139,6 @@ getMemcachedValueNoExpiry = do
   mCiphertext <- Binary.label "ciphertext" $ toStrict <$> Binary.getRemainingLazyByteString
   return MemcachedValue{..}
 
-
 memcachedAvailable :: ( MonadHandler m, HandlerSite m ~ UniWorX
                       )
                    => m Bool
@@ -143,9 +151,9 @@ data MemcachedException = MemcachedException Memcached.MemcachedException
   deriving anyclass (Exception)
 
 
-memcachedKey :: Typeable a
+toMemcachedKey :: Typeable a
              => AEAD.Key -> Proxy a -> Lazy.ByteString -> ByteString
-memcachedKey (Saltine.encode -> kmacKey) p = BA.convert . kmaclazy @(SHAKE256 256) (encodeUtf8 . tshow $ typeRep p) kmacKey
+toMemcachedKey (Saltine.encode -> kmacKey) p = BA.convert . kmaclazy @(SHAKE256 256) (encodeUtf8 . tshow $ typeRep p) kmacKey
 
 memcachedAAD :: ByteString -> Maybe POSIXTime -> ByteString
 memcachedAAD cKey mExpiry = toStrict . Binary.runPut $ do
@@ -154,18 +162,30 @@ memcachedAAD cKey mExpiry = toStrict . Binary.runPut $ do
 
 memcachedByGet :: forall a k m.
                   ( MonadHandler m, HandlerSite m ~ UniWorX
-                  , Typeable a, Binary a
+                  , Typeable a, Binary a, NFData a
                   , Binary k
                   )
                => k -> m (Maybe a)
-memcachedByGet (Binary.encode -> k) = runMaybeT $ requestCache <|> memcache
+memcachedByGet (Binary.encode -> k) = runMaybeT $ arc <|> memcache
   where
-    requestCache = MaybeT . cacheByGet $ toStrict k
+    arc = do
+      AppMemcachedLocal{..} <- MaybeT $ getsYesod appMemcachedLocal
+      res <- hoistMaybe . preview (_1 . _NFDynamic) <=< hoistMaybe <=< cachedARC' memcachedLocalARC (typeRepFingerprint . typeRep $ Proxy @a, k) $ \mPrev -> do
+        prev@((_, prevExpiry), _) <- hoistMaybe mPrev
+        $logDebugS "memcached" "Cache hit (local ARC)"
+        lift . runMaybeT $ do -- To delete from ARC upon expiry
+          for_ prevExpiry $ \expiry -> do
+            now <- liftIO getPOSIXTime
+            guard $ expiry > now
+          return prev
+      $logDebugS "memcached" "All valid (local ARC)"
+      return res
     memcache = do
-      (aeadKey, conn) <- MaybeT $ getsYesod appMemcached
-      let cKey = memcachedKey aeadKey (Proxy @a) k
+      AppMemcached{..} <- MaybeT $ getsYesod appMemcached
+      localARC <- getsYesod appMemcachedLocal
+      let cKey = toMemcachedKey memcachedKey (Proxy @a) k
 
-      encVal <- fmap toStrict . hoist liftIO . catchMaybeT (Proxy @Memcached.MemcachedException) $ Memcached.get_ cKey conn
+      encVal <- fmap toStrict . hoist liftIO . catchMaybeT (Proxy @Memcached.MemcachedException) $ Memcached.get_ cKey memcachedConn
 
       $logDebugS "memcached" "Cache hit"
 
@@ -177,11 +197,20 @@ memcachedByGet (Binary.encode -> k) = runMaybeT $ requestCache <|> memcache
               guard $ expiry > now + clockLeniency
             $logDebugS "memcached" $ "Expiry valid: " <> tshow mExpiry
             let aad = memcachedAAD cKey mExpiry
-            decrypted <- hoistMaybe $ AEAD.aeadOpen aeadKey mNonce mCiphertext aad
+            decrypted <- hoistMaybe $ AEAD.aeadOpen memcachedKey mNonce mCiphertext aad
 
             $logDebugS "memcached" $ "Decryption valid " <> bool "without" "with" doExp <> " expiration"
+      
+            let withCache = case localARC of
+                  Just AppMemcachedLocal{..} -> cachedARC memcachedLocalARC (typeRepFingerprint . typeRep $ Proxy @a, k)
+                  Nothing -> fmap (view _1) . ($ Nothing)
+            res <- hoistMaybe . preview (_1 . _NFDynamic) <=< withCache $ \case
+              Nothing -> fmap ((, length decrypted) . (, mExpiry) . review (_NFDynamic @a)) . hoistMaybe $ runGetMaybe Binary.get decrypted
+              Just p -> return p
 
-            hoistMaybe $ runGetMaybe Binary.get decrypted
+            $logDebugS "memcached" "All valid"
+
+            return res
 
       withExp True <|> withExp False
       where
@@ -194,50 +223,112 @@ memcachedByGet (Binary.encode -> k) = runMaybeT $ requestCache <|> memcache
 memcachedBySet :: forall a k m.
                   ( MonadHandler m, HandlerSite m ~ UniWorX
                   , MonadThrow m
-                  , Typeable a, Binary a
+                  , Typeable a, Binary a, NFData a
                   , Binary k
                   )
                => Maybe Expiry -> k -> a -> m ()
 memcachedBySet mExp (Binary.encode -> k) v = do
   mExp' <- for mExp $ \exp -> maybe (throwM $ MemcachedInvalidExpiry exp) return $ exp ^? _MemcachedExpiry
+
+  let decrypted = toStrict $ Binary.encode v
+  mExpiry <- for mExp $ \case
+    Left uTime -> return $ utcTimeToPOSIXSeconds uTime
+    Right diff -> liftIO $ (+ realToFrac diff) <$> getPOSIXTime
+
   mConn <- getsYesod appMemcached
-  for_ mConn $ \(aeadKey, conn) -> do
+  for_ mConn $ \AppMemcached{..} -> do
     mNonce <- liftIO AEAD.newNonce
-    mExpiry <- for mExp $ \case
-      Left uTime -> return $ utcTimeToPOSIXSeconds uTime
-      Right diff -> liftIO $ (+ realToFrac diff) <$> getPOSIXTime
-    let cKey = memcachedKey aeadKey (Proxy @a) k
+    let cKey = toMemcachedKey memcachedKey (Proxy @a) k
         aad = memcachedAAD cKey mExpiry
-        mCiphertext = AEAD.aead aeadKey mNonce (toStrict $ Binary.encode v) aad
-    liftIO $ Memcached.set zeroBits (fromMaybe zeroBits mExp') cKey (Binary.runPut $ putMemcachedValue MemcachedValue{..}) conn
-    cacheBySet (toStrict k) v
+        mCiphertext = AEAD.aead memcachedKey mNonce decrypted aad
+    liftIO $ Memcached.set zeroBits (fromMaybe zeroBits mExp') cKey (Binary.runPut $ putMemcachedValue MemcachedValue{..}) memcachedConn
     $logDebugS "memcached" $ "Cache store: " <> tshow mExpiry
 
+  mLocal <- getsYesod appMemcachedLocal
+  for_ mLocal $ \AppMemcachedLocal{..} -> do
+    void . cachedARC memcachedLocalARC (typeRepFingerprint . typeRep $ Proxy @a, k) . const $ return ((_NFDynamic # v, mExpiry), length decrypted)
+    $logDebugS "memcached" $ "Cache store: " <> tshow mExpiry <> " (local ARC)"
+    -- DEBUG
+    let inv = Base64.encode . toStrict $ Binary.encode MemcachedLocalInvalidateMsg{..}
+          where mLocalInvalidateType = typeRepFingerprint . typeRep $ Proxy @a
+                mLocalInvalidateKey = k
+    $logDebugS "memcached" $ "To invalidate remotely: " <> tshow inv
+
 memcachedByInvalidate :: forall a k m p.
                          ( MonadHandler m, HandlerSite m ~ UniWorX
                          , Typeable a
                          , Binary k
                          )
                       => k -> p a -> m ()
-memcachedByInvalidate (Binary.encode -> k) _ = maybeT_ $ do
-  (aeadKey, conn) <- MaybeT $ getsYesod appMemcached
-  let cKey = memcachedKey aeadKey (Proxy @a) k
-  hoist liftIO . catchIfMaybeT Memcached.isKeyNotFound $ Memcached.delete cKey conn
+memcachedByInvalidate (Binary.encode -> k) _ = arc >> memcache
+  where
+    memcache = maybeT_ $ do
+      AppMemcached{..} <- MaybeT $ getsYesod appMemcached
+      let cKey = toMemcachedKey memcachedKey (Proxy @a) k
+      hoist liftIO . catchIfMaybeT Memcached.isKeyNotFound $ Memcached.delete cKey memcachedConn
+      $logDebugS "memcached" "Cache invalidation"
+    arc = maybeT_ $ do
+      AppMemcachedLocal{..} <- MaybeT $ getsYesod appMemcachedLocal
+      let arcKey = (typeRepFingerprint . typeRep $ Proxy @a, k)
+      atomically $ modifyTVar' memcachedLocalInvalidationQueue (:> arcKey)
+      void . cachedARC' memcachedLocalARC arcKey . const $ return Nothing
+      $logDebugS "memcached" "Cache invalidation (local ARC)"
+
+data MemcachedLocalInvalidateMsg = MemcachedLocalInvalidateMsg
+  { mLocalInvalidateType :: Fingerprint
+  , mLocalInvalidateKey :: Lazy.ByteString
+  } deriving (Eq, Ord, Show, Typeable)
+
+instance Binary MemcachedLocalInvalidateMsg where
+  get = Binary.label "MemcachedLocalInvalidateMsg" $ do
+    mLocalInvalidateType <- Binary.label "mLocalInvalidateType" $ Fingerprint <$> Binary.getWord64le <*> Binary.getWord64le
+    mLocalInvalidateKey <- Binary.label "mLocalInvalidateKey" Binary.getRemainingLazyByteString
+    return MemcachedLocalInvalidateMsg{..}
+  put MemcachedLocalInvalidateMsg{..} = do
+    let Fingerprint w1 w2 = mLocalInvalidateType
+    Binary.putWord64le w1
+    Binary.putWord64le w2
+    Binary.putLazyByteString mLocalInvalidateKey
+  
+manageMemcachedLocalInvalidations :: ( MonadUnliftIO m
+                                     , MonadLogger m
+                                     )
+                                  => ARCHandle (Fingerprint, Lazy.ByteString) Int (NFDynamic, Maybe POSIXTime)
+                                  -> TVar (Seq (Fingerprint, Lazy.ByteString))
+                                  -> PostgresqlChannelManager m ()
+manageMemcachedLocalInvalidations localARC iQueue = PostgresqlChannelManager
+  { pgcTerminate = forever $ threadDelay maxBound
+  , pgcOnInput = Just $ \inpBS -> case Binary.runGetOrFail Binary.get . fromStrict <$> Base64.decode inpBS of
+      Right (Right (bs', _, MemcachedLocalInvalidateMsg{..})) | null bs' ->
+        void . cachedARC' localARC (mLocalInvalidateType, mLocalInvalidateKey) $ \mPrev -> do
+          $logDebugS "memcached" $ "Remote invalidation in local ARC: " <> bool "miss" "hit" (is _Just mPrev)
+          return Nothing
+      _other -> $logErrorS "memcached" $ "Received unparseable remote invalidation: " <> tshow inpBS
+  , pgcGenOutput = atomically $ do
+      iQueue' <- readTVar iQueue
+      i <- case iQueue' of
+        i :< is' -> i <$ writeTVar iQueue is'
+        _other -> mzero
+      let (mLocalInvalidateType, mLocalInvalidateKey) = i
+      return . Base64.encode . toStrict $ Binary.encode MemcachedLocalInvalidateMsg{..}
+  }
 
 
 newtype MemcachedUnkeyed a = MemcachedUnkeyed { unMemcachedUnkeyed :: a }
   deriving (Typeable)
   deriving newtype (Eq, Ord, Show, Binary)
+instance NFData a => NFData (MemcachedUnkeyed a) where
+  rnf = rnf . unMemcachedUnkeyed
 
 memcachedGet :: ( MonadHandler m, HandlerSite m ~ UniWorX
-                , Typeable a, Binary a
+                , Typeable a, Binary a, NFData a
                 )
              => m (Maybe a)
 memcachedGet = fmap unMemcachedUnkeyed <$> memcachedByGet ()
 
 memcachedSet :: ( MonadHandler m, HandlerSite m ~ UniWorX
                 , MonadThrow m
-                , Typeable a, Binary a
+                , Typeable a, Binary a, NFData a
                 )
              => Maybe Expiry -> a -> m ()
 memcachedSet mExp = memcachedBySet mExp () . MemcachedUnkeyed
@@ -260,14 +351,14 @@ memcachedWith (doGet, doSet) act = do
 
 memcached :: ( MonadHandler m, HandlerSite m ~ UniWorX
              , MonadThrow m
-             , Typeable a, Binary a
+             , Typeable a, Binary a, NFData a
              )
           => Maybe Expiry -> m a -> m a
 memcached mExp = memcachedWith (memcachedGet, \x -> x <$ memcachedSet mExp x)
 
 memcachedBy :: ( MonadHandler m, HandlerSite m ~ UniWorX
                , MonadThrow m
-               , Typeable a, Binary a
+               , Typeable a, Binary a, NFData a
                , Binary k
                )
             => Maybe Expiry -> k -> m a -> m a
@@ -277,6 +368,8 @@ memcachedBy mExp k = memcachedWith (memcachedByGet k, \x -> x <$ memcachedBySet
 newtype MemcachedUnkeyedLoc a = MemcachedUnkeyedLoc { unMemcachedUnkeyedLoc :: a }
   deriving (Typeable)
   deriving newtype (Eq, Ord, Show, Binary)
+instance NFData a => NFData (MemcachedUnkeyedLoc a) where
+  rnf MemcachedUnkeyedLoc{..} = rnf unMemcachedUnkeyedLoc
 
 memcachedHere :: Q Exp
 memcachedHere = do
@@ -286,11 +379,21 @@ memcachedHere = do
 newtype MemcachedKeyedLoc a = MemcachedKeyedLoc { unMemcachedKeyedLoc :: a }
   deriving (Typeable)
   deriving newtype (Eq, Ord, Show, Binary)
+instance NFData a => NFData (MemcachedKeyedLoc a) where
+  rnf MemcachedKeyedLoc{..} = rnf unMemcachedKeyedLoc
+
+withMemcachedKeyedLoc :: Functor f => (f (MemcachedKeyedLoc a) -> f (MemcachedKeyedLoc a)) -> (f a -> f a)
+withMemcachedKeyedLoc act = fmap unMemcachedKeyedLoc . act . fmap MemcachedKeyedLoc
+{-# INLINE withMemcachedKeyedLoc #-}
+
+withMemcachedKeyedLoc' :: (Functor f, Functor f') => (f (MemcachedKeyedLoc a) -> f (f' (MemcachedKeyedLoc a))) -> (f a -> f (f' a))
+withMemcachedKeyedLoc' act = fmap (fmap unMemcachedKeyedLoc) . act . fmap MemcachedKeyedLoc
+{-# INLINE withMemcachedKeyedLoc' #-}
 
 memcachedByHere :: Q Exp
 memcachedByHere = do
   loc <- location
-  [e| \mExp k -> fmap unMemcachedKeyedLoc . memcachedBy mExp (loc, k) . fmap MemcachedKeyedLoc |]
+  [e| \mExp k -> withMemcachedKeyedLoc (memcachedBy mExp (loc, k)) |]
 
 
 data HashableDynamic = forall a. (Hashable a, Eq a) => HashableDynamic !(TypeRep a) !a
@@ -348,7 +451,7 @@ memcachedLimitedWith (doGet, doSet) liftAct (hashableDynamic -> lK) burst rate t
 memcachedLimited :: forall a m.
                     ( MonadHandler m, HandlerSite m ~ UniWorX
                     , MonadThrow m
-                    , Typeable a, Binary a
+                    , Typeable a, Binary a, NFData a
                     )
                  => Word64 -- ^ burst-size (tokens)
                  -> Word64 -- ^ avg. inverse rate (usec/token)
@@ -361,7 +464,7 @@ memcachedLimited burst rate tokens mExp = memcachedLimitedWith (memcachedGet, me
 memcachedLimitedKey :: forall a k' m.
                        ( MonadHandler m, HandlerSite m ~ UniWorX
                        , MonadThrow m
-                       , Typeable a, Binary a
+                       , Typeable a, Binary a, NFData a
                        , Typeable k', Hashable k', Eq k'
                        )
                     => k'
@@ -376,7 +479,7 @@ memcachedLimitedKey lK burst rate tokens mExp = memcachedLimitedWith (memcachedG
 memcachedLimitedBy :: forall a k m.
                      ( MonadHandler m, HandlerSite m ~ UniWorX
                       , MonadThrow m
-                      , Typeable a, Binary a
+                      , Typeable a, Binary a, NFData a
                       , Binary k
                       )
                    => Word64 -- ^ burst-size (tokens)
@@ -391,7 +494,7 @@ memcachedLimitedBy burst rate tokens mExp k = memcachedLimitedWith (memcachedByG
 memcachedLimitedKeyBy :: forall a k' k m.
                          ( MonadHandler m, HandlerSite m ~ UniWorX
                          , MonadThrow m
-                         , Typeable a, Binary a
+                         , Typeable a, Binary a, NFData a
                          , Typeable k', Hashable k', Eq k'
                          , Binary k
                          )
@@ -418,18 +521,18 @@ memcachedLimitedKeyHere = do
 memcachedLimitedByHere :: Q Exp
 memcachedLimitedByHere = do
   loc <- location
-  [e| \burst rate tokens mExp k -> fmap (fmap unMemcachedKeyedLoc) . memcachedLimitedBy burst rate tokens mExp (loc, k) . fmap MemcachedKeyedLoc |]
+  [e| \burst rate tokens mExp k -> withMemcachedKeyedLoc' (memcachedLimitedBy burst rate tokens mExp (loc, k)) |]
 
 memcachedLimitedKeyByHere :: Q Exp
 memcachedLimitedKeyByHere = do
   loc <- location
-  [e| \lK burst rate tokens mExp k -> fmap (fmap unMemcachedKeyedLoc) . memcachedLimitedKeyBy lK burst rate tokens mExp (loc, k) . fmap MemcachedKeyedLoc |]
+  [e| \lK burst rate tokens mExp k -> withMemcachedKeyedLoc' (memcachedLimitedKeyBy lK burst rate tokens mExp (loc, k)) |]
 
 
 memcacheAuth :: forall m k a.
                 ( MonadHandler m, HandlerSite m ~ UniWorX
                 , MonadThrow m
-                , Typeable a, Binary a
+                , Typeable a, Binary a, NFData a
                 , Binary k
                 )
              => k
@@ -450,7 +553,7 @@ memcacheAuth k mx = cachedByBinary k $ do
 memcacheAuth' :: forall m k a.
                  ( MonadHandler m, HandlerSite m ~ UniWorX
                  , MonadThrow m
-                 , Typeable a, Binary a
+                 , Typeable a, Binary a, NFData a
                  , Binary k
                  )
               => Expiry
@@ -462,7 +565,7 @@ memcacheAuth' exp k = memcacheAuth k . (<* tell (Just $ Min exp)) . lift
 memcacheAuthMax :: forall m k a.
                    ( MonadHandler m, HandlerSite m ~ UniWorX
                    , MonadThrow m
-                   , Typeable a, Binary a
+                   , Typeable a, Binary a, NFData a
                    , Binary k
                    )
                 => Expiry
@@ -474,17 +577,17 @@ memcacheAuthMax exp k = memcacheAuth k . (tell (Just $ Min exp) *>)
 memcacheAuthHere :: Q Exp
 memcacheAuthHere = do
   loc <- location
-  [e| \k -> fmap unMemcachedKeyedLoc . memcacheAuth (loc, k) . fmap MemcachedKeyedLoc |]
+  [e| \k -> withMemcachedKeyedLoc (memcacheAuth (loc, k)) |]
 
 memcacheAuthHere' :: Q Exp
 memcacheAuthHere' = do
   loc <- location
-  [e| \exp k -> fmap unMemcachedKeyedLoc . memcacheAuth' exp (loc, k) . fmap MemcachedKeyedLoc |]
+  [e| \exp k -> withMemcachedKeyedLoc (memcacheAuth' exp (loc, k)) |]
   
 memcacheAuthHereMax :: Q Exp
 memcacheAuthHereMax = do
   loc <- location
-  [e| \exp k -> fmap unMemcachedKeyedLoc . memcacheAuthMax exp (loc, k) . fmap MemcachedKeyedLoc |]
+  [e| \exp k -> withMemcachedKeyedLoc (memcacheAuthMax exp (loc, k)) |]
 
 
 
@@ -576,7 +679,7 @@ memcachedTimeout :: ( MonadHandler m, HandlerSite m ~ UniWorX
                     , MonadThrow m
                     , MonadUnliftIO m
                     , Typeable k'', Hashable k'', Eq k''
-                    , Typeable a, Binary a
+                    , Typeable a, Binary a, NFData a
                     )
                  => Maybe Expiry -> DiffTime -> k'' -> m a -> m (Maybe a)
 memcachedTimeout mExp = memcachedTimeoutWith (memcachedGet, memcachedSet mExp)
@@ -585,7 +688,7 @@ memcachedTimeoutBy :: ( MonadHandler m, HandlerSite m ~ UniWorX
                       , MonadThrow m
                       , MonadUnliftIO m
                       , Typeable k'', Hashable k'', Eq k''
-                      , Typeable a, Binary a
+                      , Typeable a, Binary a, NFData a
                       , Binary k
                       )
                    => Maybe Expiry -> DiffTime -> k'' -> k -> m a -> m (Maybe a)
@@ -606,7 +709,7 @@ memcachedLimitedTimeout :: forall a k'' m.
                            , MonadThrow m
                            , MonadUnliftIO m
                            , Typeable k'', Hashable k'', Eq k''
-                           , Typeable a, Binary a
+                           , Typeable a, Binary a, NFData a
                            )
                         => Word64 -- ^ burst-size (tokens)
                         -> Word64 -- ^ avg. inverse rate (usec/token)
@@ -623,7 +726,7 @@ memcachedLimitedKeyTimeout :: forall a k' k'' m.
                               , MonadThrow m
                               , MonadUnliftIO m
                               , Typeable k'', Hashable k'', Eq k''
-                              , Typeable a, Binary a
+                              , Typeable a, Binary a, NFData a
                               , Typeable k', Hashable k', Eq k'
                               )
                            => k'
@@ -642,7 +745,7 @@ memcachedLimitedTimeoutBy :: forall a k'' k m.
                              , MonadThrow m
                              , MonadUnliftIO m
                              , Typeable k'', Hashable k'', Eq k''
-                             , Typeable a, Binary a
+                             , Typeable a, Binary a, NFData a
                              , Binary k
                              )
                           => Word64 -- ^ burst-size (tokens)
@@ -661,7 +764,7 @@ memcachedLimitedKeyTimeoutBy :: forall a k' k'' k m.
                                 , MonadThrow m
                                 , MonadUnliftIO m
                                 , Typeable k'', Hashable k'', Eq k''
-                                , Typeable a, Binary a
+                                , Typeable a, Binary a, NFData a
                                 , Typeable k', Hashable k', Eq k'
                                 , Binary k
                                 )
diff --git a/src/Import/NoModel.hs b/src/Import/NoModel.hs
index 8491e2f60..c8854d786 100644
--- a/src/Import/NoModel.hs
+++ b/src/Import/NoModel.hs
@@ -75,6 +75,9 @@ import Data.Monoid            as Import (Last(..), First(..), Any(..), All(..),
 import Data.Binary            as Import (Binary)
 import Data.Binary.Instances  as Import ()
 
+import Data.Dynamic           as Import (Dynamic)
+import Data.Dynamic.Lens      as Import
+
 import System.FilePath        as Import hiding (joinPath, normalise, isValid, makeValid)
 
 import Numeric.Natural        as Import (Natural)
diff --git a/src/Jobs/HealthReport.hs b/src/Jobs/HealthReport.hs
index a3bfb46b4..83c685700 100644
--- a/src/Jobs/HealthReport.hs
+++ b/src/Jobs/HealthReport.hs
@@ -60,7 +60,7 @@ dispatchHealthCheckMatchingClusterConfig
       dbSetting <- clusterSetting @'ClusterId
       return $ Just ourSetting == dbSetting
     clusterSettingMatches ClusterMemcachedKey = do
-      ourSetting <- getsYesod $ fmap fst . appMemcached
+      ourSetting <- getsYesod $ fmap memcachedKey . appMemcached
       dbSetting <- clusterSetting @'ClusterMemcachedKey
       return $ maybe True ((== dbSetting) . Just) ourSetting
     clusterSettingMatches ClusterVerpSecret = do
diff --git a/src/Jobs/Offload.hs b/src/Jobs/Offload.hs
index 1176823e9..8eeaf657d 100644
--- a/src/Jobs/Offload.hs
+++ b/src/Jobs/Offload.hs
@@ -2,23 +2,14 @@ module Jobs.Offload
   ( mkJobOffloadHandler
   ) where
 
-import Import hiding (bracket, js)
+import Import hiding (js)
 import Jobs.Types
 import Jobs.Queue
 
-import qualified Database.PostgreSQL.Simple as PG
-import qualified Database.PostgreSQL.Simple.Types as PG
-import qualified Database.PostgreSQL.Simple.Notification as PG
-
-import Database.Persist.Postgresql (PostgresConf, pgConnStr)
+import Utils.Postgresql
 
 import Data.Text.Encoding (decodeUtf8')
 
-import UnliftIO.Exception (bracket)
-
-
-jobOffloadChannel :: Text
-jobOffloadChannel = "job-offload"
 
 mkJobOffloadHandler :: forall m.
                        ( MonadResource m
@@ -32,39 +23,21 @@ mkJobOffloadHandler dbConf jMode
   | not shouldListen = Nothing
   | otherwise = Just $ do
       jobOffloadOutgoing <- newTVarIO mempty
-      jobOffloadHandler <- allocateAsync . bracket (liftIO . PG.connectPostgreSQL $ pgConnStr dbConf) (liftIO . PG.close) $ \pgConn -> do
-        myPid <- liftIO $ PG.getBackendPID pgConn
-
-        when shouldListen $
-          void . liftIO $ PG.execute pgConn "LISTEN ?" (PG.Only $ PG.Identifier jobOffloadChannel)
-  
-        foreverBreak $ \(($ ()) -> terminate) -> do
-          UniWorX{appJobState} <- ask
-          shouldTerminate <- atomically $ readTMVar appJobState >>= fmap not . isEmptyTMVar . jobShutdown
-          when shouldTerminate terminate
-
-          let
-            getInput = do
-              n@PG.Notification{..} <- liftIO $ PG.getNotification pgConn
-              if | notificationPid == myPid || notificationChannel /= encodeUtf8 jobOffloadChannel -> getInput
-                 | otherwise -> return n
-            getOutput = atomically $ do
-              jQueue <- readTVar jobOffloadOutgoing
-              case jQueue of
-                j :< js -> j <$ writeTVar jobOffloadOutgoing js
-                _other  -> mzero
-
-          io <- lift $ if
-            | shouldListen -> getInput `race` getOutput
-            | otherwise    -> Right <$> getOutput
-
-          case io of
-            Left PG.Notification{..}
-              | Just jId <- fromPathPiece =<< either (const Nothing) Just (decodeUtf8' notificationData)
-                -> writeJobCtl $ JobCtlPerform jId
-              | otherwise
-                -> $logErrorS "JobOffloadHandler" $ "Could not parse incoming notification data: " <> tshow notificationData
-            Right jId -> void . liftIO $ PG.execute pgConn "NOTIFY ?, ?" (PG.Identifier jobOffloadChannel, encodeUtf8 $ toPathPiece jId)
-        
+      jobOffloadHandler <- allocateAsync $ managePostgresqlChannel dbConf ChannelJobOffload PostgresqlChannelManager
+        { pgcTerminate = do
+            UniWorX{appJobState} <- ask
+            atomically $ do
+              shouldTerminate <- readTMVar appJobState >>= fmap not . isEmptyTMVar . jobShutdown
+              guardOn shouldTerminate ()
+        , pgcOnInput = Just $ \inpBS -> case fromPathPiece =<< either (const Nothing) Just (decodeUtf8' inpBS) of
+            Nothing -> $logErrorS "JobOffloadHandler" $ "Could not parse incoming notification data: " <> tshow inpBS
+            Just jId -> writeJobCtl $ JobCtlPerform jId
+        , pgcGenOutput = atomically $ do
+            jQueue <- readTVar jobOffloadOutgoing
+            j <- case jQueue of
+              j :< js -> j <$ writeTVar jobOffloadOutgoing js
+              _other  -> mzero
+            return . encodeUtf8 $ toPathPiece j
+        }
       return JobOffloadHandler{..}
   where shouldListen = has (_jobsAcceptOffload . only True) jMode
diff --git a/src/Model/Types/Security.hs b/src/Model/Types/Security.hs
index 756d69750..3e4715d61 100644
--- a/src/Model/Types/Security.hs
+++ b/src/Model/Types/Security.hs
@@ -93,7 +93,7 @@ data AuthTag -- sortiert nach gewünschter Reihenfolge auf /authpreds, d.h. Prä
   | AuthDevelopment
   | AuthFree
   deriving (Eq, Ord, Enum, Bounded, Read, Show, Data, Generic, Typeable)
-  deriving anyclass (Universe, Finite, Hashable)
+  deriving anyclass (Universe, Finite, Hashable, NFData)
 
 nullaryPathPiece ''AuthTag $ camelToPathPiece' 1
 pathPieceJSON ''AuthTag
@@ -157,7 +157,7 @@ _ReducedActiveAuthTags = iso toReducedActiveAuthTags fromReducedActiveAuthTags
 
 data PredLiteral a = PLVariable { plVar :: a } | PLNegated { plVar :: a }
   deriving (Eq, Ord, Read, Show, Data, Generic, Typeable)
-  deriving anyclass (Hashable, Binary)
+  deriving anyclass (Hashable, Binary, NFData)
 
 makeLenses_ ''PredLiteral
 makePrisms ''PredLiteral
@@ -178,7 +178,7 @@ instance PathPiece a => PathPiece (PredLiteral a) where
 
 newtype PredDNF a = PredDNF { dnfTerms :: Set (NonNull (Set (PredLiteral a))) }
   deriving (Eq, Ord, Read, Show, Data, Generic, Typeable)
-  deriving anyclass (Binary, Hashable)
+  deriving anyclass (Binary, Hashable, NFData)
 
 makeLenses_ ''PredDNF
 
diff --git a/src/Model/Types/Workflow.hs b/src/Model/Types/Workflow.hs
index 2d7a7a496..8ab3510e1 100644
--- a/src/Model/Types/Workflow.hs
+++ b/src/Model/Types/Workflow.hs
@@ -205,6 +205,7 @@ data WorkflowRole userid
   | WorkflowRoleAuthorized       { workflowRoleAuthorized   :: AuthDNF              }
   | WorkflowRoleInitiator
   deriving (Eq, Ord, Show, Read, Data, Generic, Typeable)
+  deriving anyclass (NFData)
 
 
 -----  WORKFLOW GRAPH: PAYLOAD SPECIFICATION  -----
@@ -343,7 +344,7 @@ data WorkflowScope termid schoolid courseid
   | WSTermSchool { wisTerm :: termid, wisSchool :: schoolid }
   | WSCourse { wisCourse :: courseid }
   deriving (Eq, Ord, Show, Read, Data, Generic, Typeable)
-  deriving anyclass (Hashable)
+  deriving anyclass (Hashable, NFData)
 
 data WorkflowScope'
   = WSGlobal' | WSTerm' | WSSchool' | WSTermSchool' | WSCourse'
@@ -363,6 +364,7 @@ classifyWorkflowScope = \case
 newtype WorkflowPayloadLabel = WorkflowPayloadLabel { unWorkflowPayloadLabel :: CI Text }
   deriving stock (Eq, Ord, Show, Read, Data, Generic, Typeable)
   deriving newtype (IsString, ToJSON, ToJSONKey, FromJSON, FromJSONKey, PathPiece, PersistField, Binary)
+  deriving anyclass (NFData)
 
 instance PersistFieldSql WorkflowPayloadLabel where
   sqlType _ = sqlType $ Proxy @(CI Text)
diff --git a/src/Settings.hs b/src/Settings.hs
index 9006adba0..deac6d484 100644
--- a/src/Settings.hs
+++ b/src/Settings.hs
@@ -186,6 +186,8 @@ data AppSettings = AppSettings
     , appCookieSettings         :: RegisteredCookie -> CookieSettings
 
     , appMemcachedConf          :: Maybe MemcachedConf
+    , appMemcacheAuth           :: Bool
+    , appMemcachedLocalConf     :: Maybe (ARCConf Int)
 
     , appUploadCacheConf        :: Maybe Minio.ConnectInfo
     , appUploadCacheBucket, appUploadTmpBucket :: Minio.Bucket
@@ -215,8 +217,6 @@ data AppSettings = AppSettings
     , appStudyFeaturesRecacheRelevanceWithin :: Maybe NominalDiffTime
     , appStudyFeaturesRecacheRelevanceInterval :: NominalDiffTime
 
-    , appMemcacheAuth           :: Bool
-
     , appFileSourceARCConf      :: Maybe (ARCConf Int)
     , appFileSourcePrewarmConf  :: Maybe PrewarmCacheConf
 
@@ -533,12 +533,15 @@ instance FromJSON AppSettings where
               ]
         appWidgetMemcachedConf    <- assertM validWidgetMemcachedConf <$> o .:? "widget-memcached"
         appSessionMemcachedConf   <- assertM validMemcachedConf <$> o .:? "session-memcached"
-        appMemcachedConf          <- assertM validMemcachedConf <$> o .:? "memcached"
         appRoot                   <- o .:? "approot" .!= const Nothing
         appHost                   <- fromString <$> o .: "host"
         appPort                   <- o .: "port"
         appIpFromHeader           <- o .: "ip-from-header"
 
+        appMemcachedConf          <- assertM validMemcachedConf <$> o .:? "memcached"
+        appMemcacheAuth           <- o .:? "memcache-auth" .!= False
+        appMemcachedLocalConf     <- assertM isValidARCConf <$> o .:? "memcached-local"
+
         appMailFrom               <- o .: "mail-from"
         appMailEnvelopeFrom       <- o .:? "mail-envelope-from" .!= addressEmail appMailFrom
         appMailSender             <- o .:? "mail-sender" .!= appMailFrom
@@ -654,14 +657,11 @@ instance FromJSON AppSettings where
 
         appDownloadTokenExpire <- o .: "download-token-expire"
 
-        appMemcacheAuth <- o .:? "memcache-auth" .!= False
-
         appJobMode <- o .:? "job-mode" .!= JobsLocal True
 
         appStudyFeaturesRecacheRelevanceWithin   <- o .:? "study-features-recache-relevance-within"
         appStudyFeaturesRecacheRelevanceInterval <- o .:  "study-features-recache-relevance-interval"
 
-        let isValidARCConf ARCConf{..} = arccMaximumWeight > 0
         appFileSourceARCConf <- assertM isValidARCConf <$> o .:? "file-source-arc"
 
         let isValidPrewarmConf PrewarmCacheConf{..} = and
@@ -676,6 +676,7 @@ instance FromJSON AppSettings where
         appBotMitigations <- o .:? "bot-mitigations" .!= Set.empty
 
         return AppSettings{..}
+      where isValidARCConf ARCConf{..} = arccMaximumWeight > 0
 
 makeClassy_ ''AppSettings
 
diff --git a/src/Utils/ARC.hs b/src/Utils/ARC.hs
index 0f1b94ee5..5ae8a724d 100644
--- a/src/Utils/ARC.hs
+++ b/src/Utils/ARC.hs
@@ -8,19 +8,44 @@ module Utils.ARC
   , arcRecentSize, arcFrequentSize, arcGhostRecentSize, arcGhostFrequentSize
   , getARCRecentWeight, getARCFrequentWeight
   , describeARC
+  , NFDynamic(..), _NFDynamic, DynARC, DynARCHandle
   ) where
 
 import ClassyPrelude
 
-import Data.OrdPSQ (OrdPSQ)
-import qualified Data.OrdPSQ as OrdPSQ
+import Data.HashPSQ (HashPSQ)
+import qualified Data.HashPSQ as HashPSQ
 
 import Control.Lens
 
+import Type.Reflection
+import Text.Show (showString)
+
+import Data.Hashable (Hashed, hashed)
+
 -- https://web.archive.org/web/20210115184012/https://dbs.uni-leipzig.de/file/ARC.pdf
 -- https://jaspervdj.be/posts/2015-02-24-lru-cache.html
 
 
+data NFDynamic where
+  NFDynamic :: forall a. NFData a => TypeRep a -> a -> NFDynamic
+
+_NFDynamic :: forall a. (Typeable a, NFData a) => Prism' NFDynamic a
+_NFDynamic = prism' toNFDyn fromNFDynamic
+  where
+    toNFDyn v = NFDynamic typeRep v
+    fromNFDynamic (NFDynamic t v)
+      | Just HRefl <- t `eqTypeRep` rep = Just v
+      | otherwise                       = Nothing
+      where rep = typeRep :: TypeRep a
+
+instance NFData NFDynamic where
+  rnf (NFDynamic t v) = rnfTypeRep t `seq` rnf v
+
+instance Show NFDynamic where
+  showsPrec _ (NFDynamic t _) = showString "<<" . showsPrec 0 t . showString ">>"
+
+
 newtype ARCTick = ARCTick { _getARCTick :: Word64 }
   deriving (Eq, Ord, Show, Typeable)
   deriving newtype (NFData)
@@ -28,13 +53,15 @@ newtype ARCTick = ARCTick { _getARCTick :: Word64 }
 makeLenses ''ARCTick
 
 data ARC k w v = ARC
-  { arcRecent, arcFrequent :: !(OrdPSQ k ARCTick (v, w))
-  , arcGhostRecent, arcGhostFrequent :: !(OrdPSQ k ARCTick ())
+  { arcRecent, arcFrequent :: !(HashPSQ (Hashed k) ARCTick (v, w))
+  , arcGhostRecent, arcGhostFrequent :: !(HashPSQ (Hashed k) ARCTick ())
   , arcRecentWeight, arcFrequentWeight :: !w
   , arcTargetRecent, arcMaximumWeight :: !w
   , arcMaximumGhost :: !Int
   }
 
+type DynARC k w = ARC (SomeTypeRep, k) w NFDynamic
+
 instance (NFData k, NFData w, NFData v) => NFData (ARC k w v) where
   rnf ARC{..} = rnf arcRecent
           `seq` rnf arcFrequent
@@ -50,10 +77,10 @@ describeARC :: Show w
             => ARC k w v
             -> String
 describeARC ARC{..} = intercalate ", "
-  [ "arcRecent: "         <> show (OrdPSQ.size arcRecent)
-  , "arcFrequent: "       <> show (OrdPSQ.size arcFrequent)
-  , "arcGhostRecent: "    <> show (OrdPSQ.size arcGhostRecent)
-  , "arcGhostFrequent: "  <> show (OrdPSQ.size arcGhostFrequent)
+  [ "arcRecent: "         <> show (HashPSQ.size arcRecent)
+  , "arcFrequent: "       <> show (HashPSQ.size arcFrequent)
+  , "arcGhostRecent: "    <> show (HashPSQ.size arcGhostRecent)
+  , "arcGhostFrequent: "  <> show (HashPSQ.size arcGhostFrequent)
   , "arcRecentWeight: "   <> show arcRecentWeight
   , "arcFrequentWeight: " <> show arcFrequentWeight
   , "arcTargetRecent: "   <> show arcTargetRecent
@@ -62,10 +89,10 @@ describeARC ARC{..} = intercalate ", "
   ]
 
 arcRecentSize, arcFrequentSize, arcGhostRecentSize, arcGhostFrequentSize :: ARC k w v -> Int
-arcRecentSize = OrdPSQ.size . arcRecent
-arcFrequentSize = OrdPSQ.size . arcFrequent
-arcGhostRecentSize = OrdPSQ.size . arcGhostRecent
-arcGhostFrequentSize = OrdPSQ.size . arcGhostFrequent
+arcRecentSize = HashPSQ.size . arcRecent
+arcFrequentSize = HashPSQ.size . arcFrequent
+arcGhostRecentSize = HashPSQ.size . arcGhostRecent
+arcGhostFrequentSize = HashPSQ.size . arcGhostFrequent
 
 getARCRecentWeight, getARCFrequentWeight :: ARC k w v -> w
 getARCRecentWeight = arcRecentWeight
@@ -83,10 +110,10 @@ initARC arcMaximumGhost arcMaximumWeight
   | arcMaximumWeight < 0 = error "initARC given negative maximum weight"
   | arcMaximumGhost < 0 = error "initARC given negative maximum ghost size"
   | otherwise = (, initialARCTick) ARC
-    { arcRecent = OrdPSQ.empty
-    , arcFrequent = OrdPSQ.empty
-    , arcGhostRecent = OrdPSQ.empty
-    , arcGhostFrequent = OrdPSQ.empty
+    { arcRecent = HashPSQ.empty
+    , arcFrequent = HashPSQ.empty
+    , arcGhostRecent = HashPSQ.empty
+    , arcGhostFrequent = HashPSQ.empty
     , arcRecentWeight = 0
     , arcFrequentWeight = 0
     , arcMaximumWeight
@@ -103,7 +130,7 @@ infixl 6 |-
 
   
 arcAlterF :: forall f k w v.
-             ( Ord k
+             ( Ord k, Hashable k
              , Functor f
              , Integral w
              )
@@ -112,57 +139,57 @@ arcAlterF :: forall f k w v.
           -> ARC k w v
           -> ARCTick -> f (ARC k w v, ARCTick)
 -- | Unchecked precondition: item weights are always less than `arcMaximumWeight`
-arcAlterF k f oldARC@ARC{..} now
-  | later <= initialARCTick = uncurry (arcAlterF k f) $ initARC arcMaximumGhost arcMaximumWeight
+arcAlterF unhashedK@(hashed -> k) f oldARC@ARC{..} now
+  | later <= initialARCTick = uncurry (arcAlterF unhashedK f) $ initARC arcMaximumGhost arcMaximumWeight
   | otherwise = (, later) <$> if
-    | Just (_p, x@(_, w), arcFrequent') <- OrdPSQ.deleteView k arcFrequent
+    | Just (_p, x@(_, w), arcFrequent') <- HashPSQ.deleteView k arcFrequent
       -> f (Just x) <&> \(fromMaybe x -> x'@(_, w'))
            -> let (arcFrequent'', arcFrequentWeight'', arcGhostFrequent') = evictToSize (arcMaximumWeight |- arcTargetRecent |- w') arcFrequent' (arcFrequentWeight - w) arcGhostFrequent
                in oldARC
-                    { arcFrequent = OrdPSQ.insert k now x' arcFrequent''
+                    { arcFrequent = HashPSQ.insert k now x' arcFrequent''
                     , arcFrequentWeight = arcFrequentWeight'' + w'
                     , arcGhostFrequent = arcGhostFrequent'
                     }
-    | Just (_p, x@(_, w), arcRecent') <- OrdPSQ.deleteView k arcRecent
+    | Just (_p, x@(_, w), arcRecent') <- HashPSQ.deleteView k arcRecent
       -> f (Just x) <&> \(fromMaybe x -> x'@(_, w'))
            -> let (arcFrequent', arcFrequentWeight', arcGhostFrequent') = evictToSize (arcMaximumWeight |- arcTargetRecent |- w') arcFrequent arcFrequentWeight arcGhostFrequent
                in oldARC
                     { arcRecent = arcRecent'
                     , arcRecentWeight = arcRecentWeight - w
-                    , arcFrequent = OrdPSQ.insert k now x' arcFrequent'
+                    , arcFrequent = HashPSQ.insert k now x' arcFrequent'
                     , arcFrequentWeight = arcFrequentWeight' + w'
                     , arcGhostFrequent = arcGhostFrequent'
                     }
-    | Just (_p, (), arcGhostRecent') <- OrdPSQ.deleteView k arcGhostRecent
+    | Just (_p, (), arcGhostRecent') <- HashPSQ.deleteView k arcGhostRecent
       -> f Nothing <&> \case
            Nothing -> oldARC
-             { arcGhostRecent = OrdPSQ.insert k now () arcGhostRecent'
+             { arcGhostRecent = HashPSQ.insert k now () arcGhostRecent'
              }
            Just x@(_, w)
-             -> let arcTargetRecent' = min arcMaximumWeight $ arcTargetRecent + max avgWeight (round $ toRational (OrdPSQ.size arcGhostFrequent) / toRational (OrdPSQ.size arcGhostRecent) * toRational avgWeight)
+             -> let arcTargetRecent' = min arcMaximumWeight $ arcTargetRecent + max avgWeight (round $ toRational (HashPSQ.size arcGhostFrequent) / toRational (HashPSQ.size arcGhostRecent) * toRational avgWeight)
                     (arcFrequent', arcFrequentWeight', arcGhostFrequent') = evictToSize (arcMaximumWeight |- arcTargetRecent' |- w) arcFrequent arcFrequentWeight arcGhostFrequent
                     (arcRecent', arcRecentWeight', arcGhostRecent'') = evictToSize (max arcTargetRecent' $ arcMaximumWeight |- arcFrequentWeight' |- w) arcRecent arcRecentWeight arcGhostRecent'
                  in oldARC
                       { arcRecent = arcRecent'
-                      , arcFrequent = OrdPSQ.insert k now x arcFrequent'
+                      , arcFrequent = HashPSQ.insert k now x arcFrequent'
                       , arcGhostRecent = arcGhostRecent''
                       , arcGhostFrequent = arcGhostFrequent'
                       , arcRecentWeight = arcRecentWeight'
                       , arcFrequentWeight = arcFrequentWeight' + w
                       , arcTargetRecent = arcTargetRecent'
                       }
-    | Just (_p, (), arcGhostFrequent') <- OrdPSQ.deleteView k arcGhostFrequent
+    | Just (_p, (), arcGhostFrequent') <- HashPSQ.deleteView k arcGhostFrequent
       -> f Nothing <&> \case
            Nothing -> oldARC
-             { arcGhostFrequent = OrdPSQ.insert k now () arcGhostFrequent'
+             { arcGhostFrequent = HashPSQ.insert k now () arcGhostFrequent'
              }
            Just x@(_, w)
-             -> let arcTargetRecent' = arcTargetRecent |- max avgWeight (round $ toRational (OrdPSQ.size arcGhostRecent) / toRational (OrdPSQ.size arcGhostFrequent) * toRational avgWeight)
+             -> let arcTargetRecent' = arcTargetRecent |- max avgWeight (round $ toRational (HashPSQ.size arcGhostRecent) / toRational (HashPSQ.size arcGhostFrequent) * toRational avgWeight)
                     (arcFrequent', arcFrequentWeight', arcGhostFrequent'') = evictToSize (arcMaximumWeight |- arcTargetRecent' |- w) arcFrequent arcFrequentWeight arcGhostFrequent'
                     (arcRecent', arcRecentWeight', arcGhostRecent') = evictToSize (max arcTargetRecent' $ arcMaximumWeight |- arcFrequentWeight' |- w) arcRecent arcRecentWeight arcGhostRecent
                  in oldARC
                       { arcRecent = arcRecent'
-                      , arcFrequent = OrdPSQ.insert k now x arcFrequent'
+                      , arcFrequent = HashPSQ.insert k now x arcFrequent'
                       , arcGhostRecent = arcGhostRecent'
                       , arcGhostFrequent = arcGhostFrequent''
                       , arcRecentWeight = arcRecentWeight'
@@ -171,35 +198,35 @@ arcAlterF k f oldARC@ARC{..} now
                       }
     | otherwise -> f Nothing <&> \case
         Nothing -> oldARC
-          { arcGhostRecent = OrdPSQ.insert k now () $ evictGhostToCount arcGhostRecent
+          { arcGhostRecent = HashPSQ.insert k now () $ evictGhostToCount arcGhostRecent
           }
         Just x@(_, w)
           -> let (arcRecent', arcRecentWeight', arcGhostRecent') = evictToSize (max arcTargetRecent (arcMaximumWeight |- arcFrequentWeight) |- w) arcRecent arcRecentWeight arcGhostRecent
               in oldARC
-                   { arcRecent = OrdPSQ.insert k now x arcRecent'
+                   { arcRecent = HashPSQ.insert k now x arcRecent'
                    , arcRecentWeight = arcRecentWeight' + w
                    , arcGhostRecent = arcGhostRecent'
                    }
   where
-    avgWeight = round $ toRational (arcRecentWeight + arcFrequentWeight) / toRational (OrdPSQ.size arcFrequent + OrdPSQ.size arcRecent)
+    avgWeight = round $ toRational (arcRecentWeight + arcFrequentWeight) / toRational (HashPSQ.size arcFrequent + HashPSQ.size arcRecent)
     
     later :: ARCTick
     later = over getARCTick succ now
     
-    evictToSize :: w -> OrdPSQ k ARCTick (v, w) -> w -> OrdPSQ k ARCTick () -> (OrdPSQ k ARCTick (v, w), w, OrdPSQ k ARCTick ())
+    evictToSize :: w -> HashPSQ (Hashed k) ARCTick (v, w) -> w -> HashPSQ (Hashed k) ARCTick () -> (HashPSQ (Hashed k) ARCTick (v, w), w, HashPSQ (Hashed k) ARCTick ())
     evictToSize tSize c cSize ghostC
       | cSize <= tSize = (c, cSize, ghostC)
-      | Just (k', p', (_, w'), c') <- OrdPSQ.minView c = evictToSize tSize c' (cSize - w') . evictGhostToCount $ OrdPSQ.insert k' p' () ghostC
+      | Just (k', p', (_, w'), c') <- HashPSQ.minView c = evictToSize tSize c' (cSize - w') . evictGhostToCount $ HashPSQ.insert k' p' () ghostC
       | otherwise = error "evictToSize: cannot reach required size through eviction"
 
-    evictGhostToCount :: OrdPSQ k ARCTick () -> OrdPSQ k ARCTick ()
+    evictGhostToCount :: HashPSQ (Hashed k) ARCTick () -> HashPSQ (Hashed k) ARCTick ()
     evictGhostToCount c
-      | OrdPSQ.size c <= arcMaximumGhost = c
-      | Just (_, _, _, c') <- OrdPSQ.minView c = evictGhostToCount c'
+      | HashPSQ.size c <= arcMaximumGhost = c
+      | Just (_, _, _, c') <- HashPSQ.minView c = evictGhostToCount c'
       | otherwise = error "evictGhostToCount: cannot reach required count through eviction"
 
 lookupARC :: forall k w v.
-             ( Ord k
+             ( Ord k, Hashable k
              , Integral w
              )
           => k
@@ -208,7 +235,7 @@ lookupARC :: forall k w v.
 lookupARC k = getConst . uncurry (arcAlterF k Const)
 
 insertARC :: forall k w v.
-             ( Ord k
+             ( Ord k, Hashable k
              , Integral w
              )
           => k
@@ -221,6 +248,8 @@ insertARC k newVal = (runIdentity .) . arcAlterF k (const $ pure newVal)
 newtype ARCHandle k w v = ARCHandle { _getARCHandle :: IORef (ARC k w v, ARCTick) }
   deriving (Eq, Typeable)
 
+type DynARCHandle k w = ARCHandle (SomeTypeRep, k) w NFDynamic
+
 initARCHandle :: forall k w v m.
                  ( MonadIO m
                  , Integral w
@@ -232,7 +261,7 @@ initARCHandle maxGhost maxWeight = fmap ARCHandle . newIORef $ initARC maxGhost
 
 cachedARC' :: forall k w v m.
               ( MonadIO m
-              , Ord k
+              , Ord k, Hashable k
               , Integral w
               , NFData k, NFData w, NFData v
               )
@@ -261,7 +290,7 @@ cachedARC' (ARCHandle arcVar) k f = do
 
 cachedARC :: forall k w v m.
              ( MonadIO m
-             , Ord k
+             , Ord k, Hashable k
              , Integral w
              , NFData k, NFData w, NFData v
              )
@@ -273,7 +302,7 @@ cachedARC h k f = fromMaybe (error "cachedARC: cachedARC' returned Nothing") <$>
   
 lookupARCHandle :: forall k w v m.
                    ( MonadIO m
-                   , Ord k
+                   , Ord k, Hashable k
                    , Integral w
                    )
                 => ARCHandle k w v
diff --git a/src/Utils/I18n.hs b/src/Utils/I18n.hs
index 08595630d..9f71d05dc 100644
--- a/src/Utils/I18n.hs
+++ b/src/Utils/I18n.hs
@@ -57,7 +57,7 @@ data I18n a = I18n
   , i18nFallbackLang :: Maybe Lang
   , i18nTranslations :: Map Lang a
   } deriving (Eq, Ord, Read, Show, Functor, Foldable, Traversable, Data, Generic, Typeable)
-    deriving anyclass (MonoFunctor, MonoFoldable, MonoTraversable, Binary)
+    deriving anyclass (MonoFunctor, MonoFoldable, MonoTraversable, Binary, NFData)
 type instance Element (I18n a) = a
 
 type I18nText = I18n Text
diff --git a/src/Utils/Metrics.hs b/src/Utils/Metrics.hs
index 97d26cbac..b4a7fe5c3 100644
--- a/src/Utils/Metrics.hs
+++ b/src/Utils/Metrics.hs
@@ -272,7 +272,7 @@ relabel l s (SampleGroup i t ss) = SampleGroup i t . flip map ss $ \(Sample k lb
 
 data ARCMetrics = ARCMetrics
 
-data ARCLabel = ARCFileSource
+data ARCLabel = ARCFileSource | ARCMemcachedLocal
   deriving (Eq, Ord, Read, Show, Enum, Bounded, Generic, Typeable)
   deriving anyclass (Universe, Finite)
 
diff --git a/src/Utils/Postgresql.hs b/src/Utils/Postgresql.hs
new file mode 100644
index 000000000..b9c19efbc
--- /dev/null
+++ b/src/Utils/Postgresql.hs
@@ -0,0 +1,67 @@
+module Utils.Postgresql
+  ( PostgresqlChannel(..)
+  , PostgresqlChannelManager(..)
+  , managePostgresqlChannel
+  , PostgresConf
+  ) where
+
+import Import.NoFoundation hiding (bracket)
+
+import qualified Database.PostgreSQL.Simple as PG
+import qualified Database.PostgreSQL.Simple.Types as PG
+import qualified Database.PostgreSQL.Simple.Notification as PG
+
+import Database.Persist.Postgresql (PostgresConf, pgConnStr)
+
+import UnliftIO.Exception (bracket)
+
+
+data PostgresqlChannel
+  = ChannelJobOffload
+  | ChannelMemcachedLocalInvalidation
+  deriving (Eq, Ord, Read, Show, Enum, Bounded, Generic, Typeable)
+  deriving anyclass (Universe, Finite)
+
+nullaryPathPiece ''PostgresqlChannel $ camelToPathPiece' 1
+
+
+data PostgresqlChannelManager m a = PostgresqlChannelManager
+  { pgcTerminate :: m a -- ^ Expected to block; used within `race`
+  , pgcOnInput :: Maybe (ByteString -> m ())
+  , pgcGenOutput :: m ByteString -- ^ Expected to block; used within `race`
+  }
+  
+managePostgresqlChannel :: forall m a.
+                           ( MonadUnliftIO m
+                           , MonadLogger m
+                           )
+                        => PostgresConf
+                        -> PostgresqlChannel
+                        -> PostgresqlChannelManager m a
+                        -> m a
+managePostgresqlChannel dbConf (toPathPiece -> chan) PostgresqlChannelManager{..} = bracket (liftIO . PG.connectPostgreSQL $ pgConnStr dbConf) (liftIO . PG.close) $ \pgConn -> do
+  myPid <- liftIO $ PG.getBackendPID pgConn
+  when (is _Just pgcOnInput) $
+    void . liftIO . PG.execute pgConn "LISTEN ?" . PG.Only $ PG.Identifier chan
+
+  let
+    getInput = do
+      n@PG.Notification{..} <- liftIO $ PG.getNotification pgConn
+      if | notificationPid == myPid || notificationChannel /= encodeUtf8 chan -> getInput
+         | otherwise -> return n
+
+  foreverBreak $ \terminate -> do
+    io <- lift . (pgcTerminate `race`) $ if
+      | is _Just pgcOnInput -> getInput `race` pgcGenOutput
+      | otherwise           -> Right <$> pgcGenOutput
+
+    case io of
+      Right (Left notif@PG.Notification{..}) -> do
+        $logDebugS "PGChannel" $ "Got input: " <> tshow notif
+        lift $ maybe (return ()) ($ notificationData) pgcOnInput
+      Right (Right o) -> do
+        void . liftIO $ PG.execute pgConn "NOTIFY ?, ?" (PG.Identifier chan, o)
+        $logDebugS "PGChannel" $ "Sent output: " <> tshow o
+      Left t -> do
+        $logDebugS "PGChannel" "Terminating..."
+        terminate t
diff --git a/src/Yesod/Core/Types/Instances.hs b/src/Yesod/Core/Types/Instances.hs
index 744e62256..ba60b6680 100644
--- a/src/Yesod/Core/Types/Instances.hs
+++ b/src/Yesod/Core/Types/Instances.hs
@@ -81,3 +81,4 @@ instance site ~ site' => ToWidget site (SomeMessage site') where
 
 deriving instance Generic AuthResult
 instance Binary AuthResult
+instance NFData AuthResult