diff --git a/backend/cmd/api/main.go b/backend/cmd/api/main.go
index 4a25fe2..99c1053 100644
--- a/backend/cmd/api/main.go
+++ b/backend/cmd/api/main.go
@@ -47,7 +47,7 @@ func main() {
 	}()
 
 	var deps router.Dependencies
-	db, err := database.OpenMySQL(cfg.MySQLDSN)
+	db, err := database.OpenMySQL(cfg.MySQLDSN, cfg.Log.Level)
 	if err != nil {
 		logger.Warn("mysql unavailable; database-backed APIs will return 503", zap.Error(err))
 	} else {
diff --git a/backend/internal/database/mysql.go b/backend/internal/database/mysql.go
index 7aa94c6..966e461 100644
--- a/backend/internal/database/mysql.go
+++ b/backend/internal/database/mysql.go
@@ -1,14 +1,20 @@
 package database
 
 import (
+	"log"
+	"os"
+	"strings"
 	"time"
 
 	"gorm.io/driver/mysql"
 	"gorm.io/gorm"
+	"gorm.io/gorm/logger"
 )
 
-func OpenMySQL(dsn string) (*gorm.DB, error) {
-	db, err := gorm.Open(mysql.Open(dsn), &gorm.Config{})
+func OpenMySQL(dsn string, logLevel string) (*gorm.DB, error) {
+	db, err := gorm.Open(mysql.Open(dsn), &gorm.Config{
+		Logger: newGormLogger(logLevel),
+	})
 	if err != nil {
 		return nil, err
 	}
@@ -25,3 +31,19 @@ func OpenMySQL(dsn string) (*gorm.DB, error) {
 
 	return db, nil
 }
+
+func newGormLogger(logLevel string) logger.Interface {
+	level := logger.Warn
+	if strings.EqualFold(strings.TrimSpace(logLevel), "debug") {
+		level = logger.Info
+	}
+	return logger.New(
+		log.New(os.Stdout, "\r\n", log.LstdFlags),
+		logger.Config{
+			SlowThreshold:             500 * time.Millisecond,
+			LogLevel:                  level,
+			IgnoreRecordNotFoundError: true,
+			Colorful:                  false,
+		},
+	)
+}
diff --git a/backend/migrations/000002_finance_query_indexes.sql b/backend/migrations/000002_finance_query_indexes.sql
new file mode 100644
index 0000000..3894e01
--- /dev/null
+++ b/backend/migrations/000002_finance_query_indexes.sql
@@ -0,0 +1,20 @@
+-- 为后台财务汇总、明细查询和退款统计补充复合索引。
+-- 该迁移按版本只执行一次；若手工执行，请先确认索引不存在。
+
+ALTER TABLE rental_orders
+  ADD INDEX idx_rental_orders_settled_at_id (settled_at, id);
+
+ALTER TABLE rental_orders
+  ADD INDEX idx_rental_orders_created_at_id (created_at, id);
+
+ALTER TABLE order_checkouts
+  ADD INDEX idx_order_checkouts_status_order_id_id (status, order_id, id);
+
+ALTER TABLE payment_orders
+  ADD INDEX idx_payment_orders_order_biz_status (order_id, biz_type, status);
+
+ALTER TABLE payment_orders
+  ADD INDEX idx_payment_orders_created_biz_status (created_at, biz_type, status);
+
+ALTER TABLE wallet_ledger
+  ADD INDEX idx_wallet_ledger_order_direction_biz (order_id, direction, biz_type);