diff --git a/backend/internal/infrastructure/ent.go b/backend/internal/infrastructure/ent.go
index 0e15c471..13184a83 100644
--- a/backend/internal/infrastructure/ent.go
+++ b/backend/internal/infrastructure/ent.go
@@ -5,6 +5,7 @@ package infrastructure
 import (
 	"context"
 	"database/sql"
+	"time"
 
 	"github.com/Wei-Shaw/sub2api/ent"
 	"github.com/Wei-Shaw/sub2api/internal/config"
@@ -54,7 +55,9 @@ func InitEnt(cfg *config.Config) (*ent.Client, *sql.DB, error) {
 	// 确保数据库 schema 已准备就绪。
 	// SQL 迁移文件是 schema 的权威来源（source of truth）。
 	// 这种方式比 Ent 的自动迁移更可控，支持复杂的迁移场景。
-	if err := applyMigrationsFS(context.Background(), drv.DB(), migrations.FS); err != nil {
+	migrationCtx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+	defer cancel()
+	if err := applyMigrationsFS(migrationCtx, drv.DB(), migrations.FS); err != nil {
 		_ = drv.Close() // 迁移失败时关闭驱动，避免资源泄露
 		return nil, nil, err
 	}
diff --git a/backend/internal/infrastructure/migrations_runner.go b/backend/internal/infrastructure/migrations_runner.go
index 69919a19..8477c031 100644
--- a/backend/internal/infrastructure/migrations_runner.go
+++ b/backend/internal/infrastructure/migrations_runner.go
@@ -10,6 +10,7 @@ import (
 	"io/fs"
 	"sort"
 	"strings"
+	"time"
 
 	"github.com/Wei-Shaw/sub2api/migrations"
 )
@@ -31,6 +32,7 @@ CREATE TABLE IF NOT EXISTS schema_migrations (
 // 在多实例部署场景下，该锁确保同一时间只有一个实例执行迁移。
 // 任何稳定的 int64 值都可以，只要不与同一数据库中的其他锁冲突即可。
 const migrationsAdvisoryLockID int64 = 694208311321144027
+const migrationsLockRetryInterval = 500 * time.Millisecond
 
 // ApplyMigrations 将嵌入的 SQL 迁移文件应用到指定的数据库。
 //
@@ -166,11 +168,23 @@ func applyMigrationsFS(ctx context.Context, db *sql.DB, fsys fs.FS) error {
 // Advisory Lock 是一种轻量级的锁机制，不与任何特定的数据库对象关联。
 // 它非常适合用于应用层面的分布式锁场景，如迁移序列化。
 func pgAdvisoryLock(ctx context.Context, db *sql.DB) error {
-	_, err := db.ExecContext(ctx, "SELECT pg_advisory_lock($1)", migrationsAdvisoryLockID)
-	if err != nil {
-		return fmt.Errorf("acquire migrations lock: %w", err)
+	ticker := time.NewTicker(migrationsLockRetryInterval)
+	defer ticker.Stop()
+
+	for {
+		var locked bool
+		if err := db.QueryRowContext(ctx, "SELECT pg_try_advisory_lock($1)", migrationsAdvisoryLockID).Scan(&locked); err != nil {
+			return fmt.Errorf("acquire migrations lock: %w", err)
+		}
+		if locked {
+			return nil
+		}
+		select {
+		case <-ctx.Done():
+			return fmt.Errorf("acquire migrations lock: %w", ctx.Err())
+		case <-ticker.C:
+		}
 	}
-	return nil
 }
 
 // pgAdvisoryUnlock 释放 PostgreSQL Advisory Lock。
diff --git a/backend/internal/repository/usage_log_repo.go b/backend/internal/repository/usage_log_repo.go
index 246285cf..5939c827 100644
--- a/backend/internal/repository/usage_log_repo.go
+++ b/backend/internal/repository/usage_log_repo.go
@@ -70,9 +70,6 @@ func (r *usageLogRepository) Create(ctx context.Context, log *service.UsageLog)
 	}
 
 	rateMultiplier := log.RateMultiplier
-	if rateMultiplier == 0 {
-		rateMultiplier = 1
-	}
 
 	query := `
 		INSERT INTO usage_logs (
diff --git a/backend/internal/setup/setup.go b/backend/internal/setup/setup.go
index 759b930c..5565ab91 100644
--- a/backend/internal/setup/setup.go
+++ b/backend/internal/setup/setup.go
@@ -260,7 +260,9 @@ func initializeDatabase(cfg *SetupConfig) error {
 		}
 	}()
 
-	return infrastructure.ApplyMigrations(context.Background(), db)
+	migrationCtx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+	defer cancel()
+	return infrastructure.ApplyMigrations(migrationCtx, db)
 }
 
 func createAdminUser(cfg *SetupConfig) error {
diff --git a/backend/migrations/008_seed_default_group.sql b/backend/migrations/008_seed_default_group.sql
new file mode 100644
index 00000000..44522152
--- /dev/null
+++ b/backend/migrations/008_seed_default_group.sql
@@ -0,0 +1,4 @@
+-- Seed a default group for fresh installs.
+INSERT INTO groups (name, description)
+SELECT 'default', 'Default group'
+WHERE NOT EXISTS (SELECT 1 FROM groups);