perf(migrations): index latest API key IP lookups

backend/internal/repository/migrations_runner.go

@@ -55,6 +55,8 @@ const paymentOrdersOutTradeNoUniqueMigration = "120_enforce_payment_orders_out_t
 const paymentOrdersOutTradeNoUniqueIndex = "paymentorder_out_trade_no_unique"
 const schedulerOutboxPendingDedupKeyMigration = "153_scheduler_outbox_pending_dedup_key_index_notx.sql"
 const schedulerOutboxPendingDedupKeyIndex = "idx_scheduler_outbox_pending_dedup_key"
+const latestAPIKeyIPIndexMigration = "174_add_usage_logs_api_key_latest_ip_index_notx.sql"
+const latestAPIKeyIPIndex = "idx_usage_logs_api_key_latest_ip"
 
 type migrationChecksumCompatibilityRule struct {
 	fileChecksum       string
@@ -264,6 +266,8 @@ func prepareNonTransactionalMigration(ctx context.Context, db *sql.DB, name stri
 		return preparePaymentOrdersOutTradeNoUniqueMigration(ctx, db)
 	case schedulerOutboxPendingDedupKeyMigration:
 		return dropInvalidIndexIfPresent(ctx, db, schedulerOutboxPendingDedupKeyIndex)
+	case latestAPIKeyIPIndexMigration:
+		return dropInvalidIndexIfPresent(ctx, db, latestAPIKeyIPIndex)
 	default:
 		return nil
 	}

backend/internal/repository/migrations_runner_notx_test.go

@@ -116,6 +116,45 @@ CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_t_b ON t(b);
 	require.NoError(t, mock.ExpectationsWereMet())
 }
 
+func TestApplyMigrationsFS_NonTransactionalMigration_LatestAPIKeyIPIndexDropsInvalidIndexBeforeRetry(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer func() { _ = db.Close() }()
+
+	prepareMigrationsBootstrapExpectations(mock)
+	mock.ExpectQuery("SELECT checksum FROM schema_migrations WHERE filename = \\$1").
+		WithArgs(latestAPIKeyIPIndexMigration).
+		WillReturnError(sql.ErrNoRows)
+	mock.ExpectQuery("SELECT EXISTS \\(").
+		WithArgs(latestAPIKeyIPIndex).
+		WillReturnRows(sqlmock.NewRows([]string{"exists"}).AddRow(true))
+	mock.ExpectExec("DROP INDEX CONCURRENTLY IF EXISTS idx_usage_logs_api_key_latest_ip").
+		WillReturnResult(sqlmock.NewResult(0, 0))
+	mock.ExpectExec("CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_usage_logs_api_key_latest_ip").
+		WillReturnResult(sqlmock.NewResult(0, 0))
+	mock.ExpectExec("INSERT INTO schema_migrations \\(filename, checksum\\) VALUES \\(\\$1, \\$2\\)").
+		WithArgs(latestAPIKeyIPIndexMigration, sqlmock.AnyArg()).
+		WillReturnResult(sqlmock.NewResult(1, 1))
+	mock.ExpectExec("SELECT pg_advisory_unlock\\(\\$1\\)").
+		WithArgs(migrationsAdvisoryLockID).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	fsys := fstest.MapFS{
+		latestAPIKeyIPIndexMigration: &fstest.MapFile{
+			Data: []byte(`
+CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_usage_logs_api_key_latest_ip
+    ON usage_logs (api_key_id, created_at DESC, id DESC)
+    INCLUDE (ip_address)
+    WHERE ip_address IS NOT NULL AND ip_address <> '';
+`),
+		},
+	}
+
+	err = applyMigrationsFS(context.Background(), db, fsys)
+	require.NoError(t, err)
+	require.NoError(t, mock.ExpectationsWereMet())
+}
+
 func TestApplyMigrationsFS_PaymentOrdersOutTradeNoUniqueMigration_FailsFastOnDuplicatePrecheck(t *testing.T) {
 	db, mock, err := sqlmock.New()
 	require.NoError(t, err)

backend/migrations/174_add_usage_logs_api_key_latest_ip_index_notx.sql

@@ -0,0 +1,5 @@
+-- Support the per-key latest non-empty source IP lookup without scanning full key history.
+CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_usage_logs_api_key_latest_ip
+    ON usage_logs (api_key_id, created_at DESC, id DESC)
+    INCLUDE (ip_address)
+    WHERE ip_address IS NOT NULL AND ip_address <> '';

backend/migrations/latest_api_key_ip_index_test.go

@@ -0,0 +1,19 @@
+package migrations
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestLatestAPIKeyIPIndexMigration(t *testing.T) {
+	content, err := FS.ReadFile("174_add_usage_logs_api_key_latest_ip_index_notx.sql")
+	require.NoError(t, err)
+
+	sql := strings.Join(strings.Fields(string(content)), " ")
+	require.Contains(t, sql, "CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_usage_logs_api_key_latest_ip")
+	require.Contains(t, sql, "ON usage_logs (api_key_id, created_at DESC, id DESC)")
+	require.Contains(t, sql, "INCLUDE (ip_address)")
+	require.Contains(t, sql, "WHERE ip_address IS NOT NULL AND ip_address <> ''")
+}