diff --git a/Hash2Pub.cabal b/Hash2Pub.cabal
index 2953d97..5e8d25d 100644
--- a/Hash2Pub.cabal
+++ b/Hash2Pub.cabal
@@ -46,7 +46,7 @@ category:            Network
 extra-source-files:  CHANGELOG.md
 
 common deps
-  build-depends:       base ^>=4.12.0.0, containers ^>=0.6.0.1, bytestring, utf8-string ^>=1.0.1.1, network ^>=2.8.0.1, time ^>=1.8.0.2, cmdargs ^>= 0.10, cryptonite ^>= 0.25, memory, async, stm, asn1-encoding, asn1-types, asn1-parse, publicsuffix, network-byte-order, safe, iproute, mtl, random, servant, servant-server, servant-client, warp, text, unordered-containers, hashable, unicode-transforms, http-client, http-types, unbounded-delays
+  build-depends:       base ^>=4.12.0.0, containers ^>=0.6.0.1, bytestring, utf8-string ^>=1.0.1.1, network ^>=2.8.0.1, time ^>=1.8.0.2, cmdargs ^>= 0.10, cryptonite ^>= 0.25, memory, async, stm, asn1-encoding, asn1-types, asn1-parse, publicsuffix, network-byte-order, safe, iproute, mtl, random, servant, servant-server, servant-client, warp, text, unordered-containers, hashable, unicode-transforms, http-client, http-types, unbounded-delays, dlist
   ghc-options:         -Wall -Wpartial-fields -O2
 
 
diff --git a/src/Hash2Pub/PostService.hs b/src/Hash2Pub/PostService.hs
index 099855d..c556d7f 100644
--- a/src/Hash2Pub/PostService.hs
+++ b/src/Hash2Pub/PostService.hs
@@ -17,6 +17,7 @@ import           Control.Monad.IO.Class    (liftIO)
 import           Data.Bifunctor
 import qualified Data.ByteString.Lazy.UTF8 as BSUL
 import qualified Data.ByteString.UTF8      as BSU
+import qualified Data.DList                as D
 import           Data.Either               (rights)
 import qualified Data.HashMap.Strict       as HMap
 import qualified Data.HashSet              as HSet
@@ -39,6 +40,7 @@ import           Servant.Client
 import           Hash2Pub.FediChordTypes
 import           Hash2Pub.PostService.API
 import           Hash2Pub.RingMap
+import           Hash2Pub.Utils
 
 
 data PostService d = PostService
@@ -612,27 +614,43 @@ fetchTagPosts serv = forever $ do
              pure ()
 
 
+-- TODO: make configurable
+numParallelDeliveries = 10
+
 -- TODO: paralellelisation
--- TODO: make sure it doesn't busy-wait
 relayWorker :: PostService d -> IO ()
 relayWorker serv = forever $ do
-    subscriptionMap <- readTVarIO $ subscribers serv
-    -- for each tag, try to deliver some posts to subscriber
-    forM_ subscriptionMap (\(subscriberMapSTM, _, tag) -> do
-        subscriberMap <- readTVarIO subscriberMapSTM
-        forM_ (HMap.toList subscriberMap) (\((subHost, subPort), (postChan, _)) -> do
-            postsToDeliver <- readUpTo 500 postChan
-            response <- runClientM (tagDeliveryClient tag (Txt.unlines postsToDeliver)) (mkClientEnv (httpMan serv) (BaseUrl Http subHost (fromIntegral subPort) ""))
-            -- so far just dropping failed attempts, TODO: retry mechanism
-            -- TODO: stats
-            pure ()
-            )
-        )
+    -- atomically (to be able to retry) fold a list of due delivery actions
+    jobsToProcess <- atomically $ do
+        subscriptionMap <- readTVar $ subscribers serv
+        jobList <- D.toList <$> foldM (\jobAcc (subscriberMapSTM, _, tag) -> do
+            subscriberMap <- readTVar subscriberMapSTM
+            foldM (\jobAcc' ((subHost, subPort), (postChan, _)) -> do
+                postsToDeliver <- readUpTo 500 postChan
+                -- append fetch job to job list
+                pure $ if not (null postsToDeliver)
+                   then jobAcc' `D.snoc` runClientM (tagDeliveryClient tag (Txt.unlines postsToDeliver)) (mkClientEnv (httpMan serv) (BaseUrl Http subHost (fromIntegral subPort) ""))
+                   else jobAcc'
+                ) jobAcc $ HMap.toList subscriberMap
+            ) D.empty subscriptionMap
+        -- if no relay jobs, then retry
+        if null jobList
+           then retry
+           else pure jobList
+
+    -- when processing the list, send several deliveries in parallel
+    forM_ (chunksOf numParallelDeliveries jobsToProcess) $ \jobset -> do
+        runningJobs <- mapM async jobset
+        -- so far just dropping failed attempts, TODO: retry mechanism
+        successfulResults <- rights <$> mapM waitCatch runningJobs
+        -- TODO: stats
+        pure ()
+
   where
-      readUpTo :: Int -> TChan a -> IO [a]
+      readUpTo :: Int -> TChan a -> STM [a]
       readUpTo 0 _ = pure []
       readUpTo n chan = do
-          readFromChan <- atomically (tryReadTChan chan)
+          readFromChan <- tryReadTChan chan
           case readFromChan of
                Nothing -> pure []
                Just val -> do