diff --git a/api/migrations/versions/2024_11_12_0925-01d6889832f7_add_created_at_index_for_messages.py b/api/migrations/versions/2024_11_12_0925-01d6889832f7_add_created_at_index_for_messages.py
new file mode 100644
index 0000000000..d94508edcf
--- /dev/null
+++ b/api/migrations/versions/2024_11_12_0925-01d6889832f7_add_created_at_index_for_messages.py
@@ -0,0 +1,31 @@
+"""add_created_at_index_for_messages
+
+Revision ID: 01d6889832f7
+Revises: 09a8d1878d9b
+Create Date: 2024-11-12 09:25:05.527827
+
+"""
+from alembic import op
+import models as models
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '01d6889832f7'
+down_revision = '09a8d1878d9b'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table('messages', schema=None) as batch_op:
+        batch_op.create_index('message_created_at_idx', ['created_at'], unique=False)
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table('messages', schema=None) as batch_op:
+        batch_op.drop_index('message_created_at_idx')
+    # ### end Alembic commands ###
diff --git a/api/schedule/clean_messages.py b/api/schedule/clean_messages.py
index 60de154b41..72ee2a8901 100644
--- a/api/schedule/clean_messages.py
+++ b/api/schedule/clean_messages.py
@@ -2,23 +2,32 @@ import datetime
 import time
 
 import click
+from werkzeug.exceptions import NotFound
 
 import app
 from configs import dify_config
-from core.rag.datasource.vdb.tidb_on_qdrant.tidb_service import TidbService
 from extensions.ext_database import db
-from models.account import Tenant
-from models.model import App, Message, MessageAgentThought, MessageAnnotation, MessageChain, MessageFeedback, MessageFile
+from extensions.ext_redis import redis_client
+from models.model import (
+    App,
+    Message,
+    MessageAgentThought,
+    MessageAnnotation,
+    MessageChain,
+    MessageFeedback,
+    MessageFile,
+)
 from models.web import SavedMessage
 from services.feature_service import FeatureService
-from extensions.ext_redis import redis_client
-from werkzeug.exceptions import NotFound
+
 
 @app.celery.task(queue="dataset")
 def clean_messages():
     click.echo(click.style("Start clean messages.", fg="green"))
     start_at = time.perf_counter()
-    plan_sandbox_clean_message_day = datetime.datetime.now() - datetime.timedelta(days=dify_config.PLAN_SANDBOX_CLEAN_MESSAGE_DAY_SETTING)
+    plan_sandbox_clean_message_day = datetime.datetime.now() - datetime.timedelta(
+        days=dify_config.PLAN_SANDBOX_CLEAN_MESSAGE_DAY_SETTING
+    )
     page = 1
     while True:
         try:
@@ -35,7 +44,7 @@ def clean_messages():
         if messages.items is None or len(messages.items) == 0:
             break
         for message in messages.items:
-            app = App.query.filter_by(id=message.app_id).first()      
+            app = App.query.filter_by(id=message.app_id).first()
             features_cache_key = f"features:{app.tenant_id}"
             plan_cache = redis_client.get(features_cache_key)
             if plan_cache is None:
@@ -52,12 +61,18 @@ def clean_messages():
                 db.session.query(MessageAnnotation).filter(MessageAnnotation.message_id == message.id).delete(
                     synchronize_session=False
                 )
-                db.session.query(MessageChain).filter(MessageChain.message_id == message.id).delete(synchronize_session=False)
+                db.session.query(MessageChain).filter(MessageChain.message_id == message.id).delete(
+                    synchronize_session=False
+                )
                 db.session.query(MessageAgentThought).filter(MessageAgentThought.message_id == message.id).delete(
                     synchronize_session=False
                 )
-                db.session.query(MessageFile).filter(MessageFile.message_id == message.id).delete(synchronize_session=False)
-                db.session.query(SavedMessage).filter(SavedMessage.message_id == message.id).delete(synchronize_session=False)
+                db.session.query(MessageFile).filter(MessageFile.message_id == message.id).delete(
+                    synchronize_session=False
+                )
+                db.session.query(SavedMessage).filter(SavedMessage.message_id == message.id).delete(
+                    synchronize_session=False
+                )
                 db.session.query(Message).filter(Message.id == message.id).delete()
                 db.session.commit()
     end_at = time.perf_counter()