diff --git a/db/post_migrate/20250904012006_prepare_tmp_idx_events_where_project_target_type_missing.rb b/db/post_migrate/20250904012006_prepare_tmp_idx_events_where_project_target_type_missing.rb
new file mode 100644
index 0000000000000000000000000000000000000000..7a4a70f28129f2cd381e617c8f431d14d9e1bf97
--- /dev/null
+++ b/db/post_migrate/20250904012006_prepare_tmp_idx_events_where_project_target_type_missing.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+class PrepareTmpIdxEventsWhereProjectTargetTypeMissing < Gitlab::Database::Migration[2.3]
+  milestone '18.4'
+
+  INDEX_NAME = :tmp_idx_events_where_project_target_type_missing
+  PROJECT_ACTIONS = [1, 5, 8, 9, 11].freeze # Defined in `/app/models/event.rb`
+
+  def up
+    # rubocop:disable Migration/PreventIndexCreation -- temporary index for https://gitlab.com/gitlab-org/gitlab/-/issues/565788
+    prepare_async_index(
+      :events, :id,
+      where: "target_type IS NULL AND action IN (#{PROJECT_ACTIONS.join(',')}) AND project_id IS NOT NULL",
+      name: INDEX_NAME
+    )
+    # rubocop:enable Migration/PreventIndexCreation
+  end
+
+  def down
+    unprepare_async_index_by_name :events, INDEX_NAME
+  end
+end
diff --git a/db/schema_migrations/20250904012006 b/db/schema_migrations/20250904012006
new file mode 100644
index 0000000000000000000000000000000000000000..fb35178dc89edf120033aa71399be75642c63811
--- /dev/null
+++ b/db/schema_migrations/20250904012006
@@ -0,0 +1 @@
+3894e3e2c419f341ea7e58cffbac542fcf6cd930b954d0230041da412e8000ad
\ No newline at end of file