diff --git a/chat_box/migrations/0012_auto_20230308_1417.py b/chat_box/migrations/0012_auto_20230308_1417.py
new file mode 100644
index 0000000..bd3ec5a
--- /dev/null
+++ b/chat_box/migrations/0012_auto_20230308_1417.py
@@ -0,0 +1,34 @@
+# Generated by Django 3.2.18 on 2023-03-08 07:17
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("judge", "0154_add_submission_indexes"),
+        ("chat_box", "0011_alter_message_hidden"),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name="message",
+            options={
+                "ordering": ("-id",),
+                "verbose_name": "message",
+                "verbose_name_plural": "messages",
+            },
+        ),
+        migrations.AlterField(
+            model_name="message",
+            name="hidden",
+            field=models.BooleanField(default=False, verbose_name="is hidden"),
+        ),
+        migrations.AddIndex(
+            model_name="message",
+            index=models.Index(
+                fields=["hidden", "room", "-id"], name="chat_box_me_hidden_b2307a_idx"
+            ),
+        ),
+    ]
diff --git a/chat_box/models.py b/chat_box/models.py
index 2dc2cb1..61e39a6 100644
--- a/chat_box/models.py
+++ b/chat_box/models.py
@@ -31,7 +31,7 @@ class Message(models.Model):
     author = models.ForeignKey(Profile, verbose_name=_("user"), on_delete=CASCADE)
     time = models.DateTimeField(verbose_name=_("posted time"), auto_now_add=True)
     body = models.TextField(verbose_name=_("body of comment"), max_length=8192)
-    hidden = models.BooleanField(verbose_name="is hidden", default=False, db_index=True)
+    hidden = models.BooleanField(verbose_name="is hidden", default=False)
     room = models.ForeignKey(
         Room, verbose_name="room id", on_delete=CASCADE, default=None, null=True
     )
@@ -44,7 +44,10 @@ class Message(models.Model):
     class Meta:
         verbose_name = "message"
         verbose_name_plural = "messages"
-        ordering = ("-time",)
+        ordering = ("-id",)
+        indexes = [
+            models.Index(fields=["hidden", "room", "-id"]),
+        ]
 
 
 class UserRoom(models.Model):