diff --git a/zerver/migrations/0693_add_conditional_indexes_for_topic.py b/zerver/migrations/0693_add_conditional_indexes_for_topic.py
new file mode 100644
index 0000000000..53ff12a5e6
--- /dev/null
+++ b/zerver/migrations/0693_add_conditional_indexes_for_topic.py
@@ -0,0 +1,61 @@
+import django.db.models.functions.text
+from django.contrib.postgres.operations import AddIndexConcurrently
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    atomic = False
+
+    dependencies = [
+        ("zerver", "0692_alter_message_is_channel_message"),
+    ]
+
+    operations = [
+        migrations.RenameIndex(
+            model_name="message",
+            new_name="zerver_message_realm_upper_subject_all",
+            old_name="zerver_message_realm_upper_subject",
+        ),
+        migrations.RenameIndex(
+            model_name="message",
+            new_name="zerver_message_realm_recipient_upper_subject_all",
+            old_name="zerver_message_realm_recipient_upper_subject",
+        ),
+        migrations.RenameIndex(
+            model_name="message",
+            new_name="zerver_message_realm_recipient_subject_all",
+            old_name="zerver_message_realm_recipient_subject",
+        ),
+        AddIndexConcurrently(
+            model_name="message",
+            index=models.Index(
+                models.F("realm_id"),
+                django.db.models.functions.text.Upper("subject"),
+                models.OrderBy(models.F("id"), descending=True, nulls_last=True),
+                condition=models.Q(("is_channel_message", True)),
+                name="zerver_message_realm_upper_subject",
+            ),
+        ),
+        AddIndexConcurrently(
+            model_name="message",
+            index=models.Index(
+                models.F("realm_id"),
+                models.F("recipient_id"),
+                django.db.models.functions.text.Upper("subject"),
+                models.OrderBy(models.F("id"), descending=True, nulls_last=True),
+                condition=models.Q(("is_channel_message", True)),
+                name="zerver_message_realm_recipient_upper_subject",
+            ),
+        ),
+        AddIndexConcurrently(
+            model_name="message",
+            index=models.Index(
+                models.F("realm_id"),
+                models.F("recipient_id"),
+                models.F("subject"),
+                models.OrderBy(models.F("id"), descending=True, nulls_last=True),
+                condition=models.Q(("is_channel_message", True)),
+                name="zerver_message_realm_recipient_subject",
+            ),
+        ),
+    ]
diff --git a/zerver/models/messages.py b/zerver/models/messages.py
index a79bb7b777..9def87c474 100644
--- a/zerver/models/messages.py
+++ b/zerver/models/messages.py
@@ -205,6 +205,29 @@ class Message(AbstractMessage):
                 "date_sent",
                 name="zerver_message_realm_date_sent",
             ),
+            models.Index(
+                # To be removed shortly
+                "realm_id",
+                Upper("subject"),
+                F("id").desc(nulls_last=True),
+                name="zerver_message_realm_upper_subject_all",
+            ),
+            models.Index(
+                # To be removed shortly
+                "realm_id",
+                "recipient_id",
+                Upper("subject"),
+                F("id").desc(nulls_last=True),
+                name="zerver_message_realm_recipient_upper_subject_all",
+            ),
+            models.Index(
+                # To be removed shortly
+                "realm_id",
+                "recipient_id",
+                "subject",
+                F("id").desc(nulls_last=True),
+                name="zerver_message_realm_recipient_subject_all",
+            ),
             models.Index(
                 # For users searching by topic (but not stream), which
                 # is done case-insensitively
@@ -212,6 +235,7 @@ class Message(AbstractMessage):
                 Upper("subject"),
                 F("id").desc(nulls_last=True),
                 name="zerver_message_realm_upper_subject",
+                condition=Q(is_channel_message=True),
             ),
             models.Index(
                 # Most stream/topic searches are case-insensitive by
@@ -223,6 +247,7 @@ class Message(AbstractMessage):
                 Upper("subject"),
                 F("id").desc(nulls_last=True),
                 name="zerver_message_realm_recipient_upper_subject",
+                condition=Q(is_channel_message=True),
             ),
             models.Index(
                 # Used by already_sent_mirrored_message_id, and when
@@ -233,6 +258,7 @@ class Message(AbstractMessage):
                 "subject",
                 F("id").desc(nulls_last=True),
                 name="zerver_message_realm_recipient_subject",
+                condition=Q(is_channel_message=True),
             ),
             models.Index(
                 # Only used by update_first_visible_message_id