diff --git a/apps/emqx_durable_storage/src/emqx_ds_replication_layer_egress.erl b/apps/emqx_durable_storage/src/emqx_ds_replication_layer_egress.erl
index 6d879dbb6..128aeb380 100644
--- a/apps/emqx_durable_storage/src/emqx_ds_replication_layer_egress.erl
+++ b/apps/emqx_durable_storage/src/emqx_ds_replication_layer_egress.erl
@@ -161,12 +161,13 @@ do_flush(
 ) ->
     case emqx_ds_replication_layer:ra_store_batch(DB, Shard, lists:reverse(Messages)) of
         ok ->
-            lists:foreach(fun(From) -> gen_server:reply(From, ok) end, Replies),
-            true = erlang:garbage_collect(),
             ?tp(
                 emqx_ds_replication_layer_egress_flush,
                 #{db => DB, shard => Shard, batch => Messages}
-            );
+            ),
+            lists:foreach(fun(From) -> gen_server:reply(From, ok) end, Replies),
+            true = erlang:garbage_collect(),
+            ok;
         Error ->
             true = erlang:garbage_collect(),
             ?tp(
@@ -175,7 +176,11 @@ do_flush(
                 #{db => DB, shard => Shard, reason => Error}
             ),
             Cooldown = ?COOLDOWN_MIN + rand:uniform(?COOLDOWN_MAX - ?COOLDOWN_MIN),
-            ok = timer:sleep(Cooldown)
+            ok = timer:sleep(Cooldown),
+            %% Since we drop the entire batch here, we at least reply callers with an
+            %% error so they don't hang indefinitely in the `gen_server' call with
+            %% `infinity' timeout.
+            lists:foreach(fun(From) -> gen_server:reply(From, {error, Error}) end, Replies)
     end,
     S#s{
         n = 0,
@@ -193,14 +198,6 @@ do_enqueue(From, Sync, MsgOrBatch, S0 = #s{n = N, batch = Batch, pending_replies
             Msg ->
                 S0#s{n = N + 1, batch = [Msg | Batch]}
         end,
-    S2 =
-        case N >= NMax of
-            true ->
-                _ = erlang:cancel_timer(S0#s.tref),
-                do_flush(S1);
-            false ->
-                S1
-        end,
     %% TODO: later we may want to delay the reply until the message is
     %% replicated, but it requies changes to the PUBACK/PUBREC flow to
     %% allow for async replies. For now, we ack when the message is
@@ -208,12 +205,20 @@ do_enqueue(From, Sync, MsgOrBatch, S0 = #s{n = N, batch = Batch, pending_replies
     %%
     %% Otherwise, the client would freeze for at least flush interval,
     %% or until the buffer is filled.
-    S =
+    S2 =
         case Sync of
             true ->
-                S2#s{pending_replies = [From | Replies]};
+                S1#s{pending_replies = [From | Replies]};
             false ->
                 gen_server:reply(From, ok),
+                S1
+        end,
+    S =
+        case N >= NMax of
+            true ->
+                _ = erlang:cancel_timer(S2#s.tref),
+                do_flush(S2);
+            false ->
                 S2
         end,
     %% TODO: add a backpressure mechanism for the server to avoid