diff --git a/payphone/cogs/calls/cog.py b/payphone/cogs/calls/cog.py
index 3716410..339bb43 100644
--- a/payphone/cogs/calls/cog.py
+++ b/payphone/cogs/calls/cog.py
@@ -86,24 +86,30 @@ class Calls(base.Cog):
             await redis.srem(constants.CHANNELS_ONCALL_SET, *hung_up_channel_ids)
 
     @tasks.loop(seconds=15)
-    async def flush_messages(self) -> None:
-        """Fetches all the pending messages from Redis and flushes them to the DB."""
+    async def flush_messages(self, all_calls: bool = False) -> None:
+        """Fetches all the pending messages from Redis and flushes them to the DB.
 
-        pipe = redis.pipeline()
+        Args:
+            all_calls (bool, optional): Whether to flush the messages for all calls of all shards.
+        """
 
-        pipe.smembers(constants.CALL_IDS_TO_FLUSH)
-        pipe.delete(constants.CALL_IDS_TO_FLUSH)
-
-        call_ids, _ = await pipe.execute()
+        call_ids = await redis.smembers(constants.CALL_IDS_TO_FLUSH)
 
         # Redis returns bytes.
-        call_ids = [int(call_id) for call_id in call_ids]
-
-        pipe = redis.pipeline()
+        call_ids = [
+            int(call_id)
+            for call_id in call_ids
+            if all_calls
+            or (int(call_id) % self.bot.shard_count) - self.bot.shard_ids[0] == 0
+        ]
 
         if len(call_ids) == 0:
             return
 
+        await redis.srem(constants.CALL_IDS_TO_FLUSH, *call_ids)
+
+        pipe = redis.pipeline()
+
         for call_id in call_ids:
             pipe.hgetall(constants.CALL_MESSAGES_TEMPLATE % call_id)
             pipe.hgetall(constants.CALL_MESSAGE_CONTENTS_TEMPLATE % call_id)
@@ -140,7 +146,7 @@ class Calls(base.Cog):
 
             for _ in range(3):
                 try:
-                    await models.Message.bulk_create(message_rows, batch_size=500)
+                    await models.Message.bulk_create(message_rows, batch_size=20)
                     break
 
                 except (
@@ -152,7 +158,7 @@ class Calls(base.Cog):
             for _ in range(3):
                 try:
                     await models.MessageContent.bulk_create(
-                        message_content_rows, batch_size=500
+                        message_content_rows, batch_size=20
                     )
                     break