diff --git a/db/docs/namespaces.yml b/db/docs/namespaces.yml
index 4010858ce5adf5d864398470422eb9db1b92db63..8fa7c2a3d3182427fa79cf9dfe2424a6cf35cec5 100644
--- a/db/docs/namespaces.yml
+++ b/db/docs/namespaces.yml
@@ -15,3 +15,6 @@ schema_inconsistencies:
 - type: missing_indexes
   object_name: index_namespaces_on_created_at
   introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/134948
+- type: missing_indexes
+  object_name: index_namespaces_on_ldap_sync_last_successful_update_at
+  introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/135040
diff --git a/db/migrate/20231109133153_drop_idx_namespaces_on_ldap_sync_last_successful_update_at_for_gitlab.rb b/db/migrate/20231109133153_drop_idx_namespaces_on_ldap_sync_last_successful_update_at_for_gitlab.rb
new file mode 100644
index 0000000000000000000000000000000000000000..1d171e3285cfa06103af66c5318df1b13efa9315
--- /dev/null
+++ b/db/migrate/20231109133153_drop_idx_namespaces_on_ldap_sync_last_successful_update_at_for_gitlab.rb
@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+class DropIdxNamespacesOnLdapSyncLastSuccessfulUpdateAtForGitlab < Gitlab::Database::Migration[2.2]
+  milestone '16.6'
+
+  disable_ddl_transaction!
+
+  TABLE_NAME = :namespaces
+  INDEX_NAME = :index_namespaces_on_ldap_sync_last_successful_update_at
+
+  def up
+    return unless should_run?
+
+    remove_concurrent_index_by_name TABLE_NAME, INDEX_NAME
+  end
+
+  def down
+    return unless should_run?
+
+    add_concurrent_index TABLE_NAME, :ldap_sync_last_successful_update_at, name: INDEX_NAME
+  end
+
+  private
+
+  def should_run?
+    Gitlab.com_except_jh?
+  end
+end
diff --git a/db/schema_migrations/20231109133153 b/db/schema_migrations/20231109133153
new file mode 100644
index 0000000000000000000000000000000000000000..c9cfd53a77d5450b8315f9d4d527c3809de23bb0
--- /dev/null
+++ b/db/schema_migrations/20231109133153
@@ -0,0 +1 @@
+fb17684ac5976811bd08e4a2edb3b3c45baaf293ee3c04e986ae3c197c59c54a
\ No newline at end of file