diff --git a/backend/internal/handler/api_key_handler.go b/backend/internal/handler/api_key_handler.go
index 24152bed..9717194b 100644
--- a/backend/internal/handler/api_key_handler.go
+++ b/backend/internal/handler/api_key_handler.go
@@ -29,11 +29,11 @@ func NewAPIKeyHandler(apiKeyService *service.APIKeyService) *APIKeyHandler {
 // CreateAPIKeyRequest represents the create API key request payload
 type CreateAPIKeyRequest struct {
 	Name          string   `json:"name" binding:"required"`
-	GroupID       *int64   `json:"group_id"`       // nullable
-	CustomKey     *string  `json:"custom_key"`     // 可选的自定义key
-	IPWhitelist   []string `json:"ip_whitelist"`   // IP 白名单
-	IPBlacklist   []string `json:"ip_blacklist"`   // IP 黑名单
-	Quota         *float64 `json:"quota"`          // 配额限制 (USD)
+	GroupID       *int64   `json:"group_id"`        // nullable
+	CustomKey     *string  `json:"custom_key"`      // 可选的自定义key
+	IPWhitelist   []string `json:"ip_whitelist"`    // IP 白名单
+	IPBlacklist   []string `json:"ip_blacklist"`    // IP 黑名单
+	Quota         *float64 `json:"quota"`           // 配额限制 (USD)
 	ExpiresInDays *int     `json:"expires_in_days"` // 过期天数
 }
 
diff --git a/backend/internal/handler/dto/types.go b/backend/internal/handler/dto/types.go
index 639766e3..af659f39 100644
--- a/backend/internal/handler/dto/types.go
+++ b/backend/internal/handler/dto/types.go
@@ -32,19 +32,19 @@ type AdminUser struct {
 }
 
 type APIKey struct {
-	ID          int64     `json:"id"`
-	UserID      int64     `json:"user_id"`
-	Key         string    `json:"key"`
-	Name        string    `json:"name"`
-	GroupID     *int64    `json:"group_id"`
-	Status      string    `json:"status"`
-	IPWhitelist []string  `json:"ip_whitelist"`
-	IPBlacklist []string  `json:"ip_blacklist"`
-	Quota       float64   `json:"quota"`       // Quota limit in USD (0 = unlimited)
-	QuotaUsed   float64   `json:"quota_used"`  // Used quota amount in USD
+	ID          int64      `json:"id"`
+	UserID      int64      `json:"user_id"`
+	Key         string     `json:"key"`
+	Name        string     `json:"name"`
+	GroupID     *int64     `json:"group_id"`
+	Status      string     `json:"status"`
+	IPWhitelist []string   `json:"ip_whitelist"`
+	IPBlacklist []string   `json:"ip_blacklist"`
+	Quota       float64    `json:"quota"`      // Quota limit in USD (0 = unlimited)
+	QuotaUsed   float64    `json:"quota_used"` // Used quota amount in USD
 	ExpiresAt   *time.Time `json:"expires_at"` // Expiration time (nil = never expires)
-	CreatedAt   time.Time `json:"created_at"`
-	UpdatedAt   time.Time `json:"updated_at"`
+	CreatedAt   time.Time  `json:"created_at"`
+	UpdatedAt   time.Time  `json:"updated_at"`
 
 	User  *User  `json:"user,omitempty"`
 	Group *Group `json:"group,omitempty"`
diff --git a/backend/internal/server/api_contract_test.go b/backend/internal/server/api_contract_test.go
index 49a7e0e4..134f6139 100644
--- a/backend/internal/server/api_contract_test.go
+++ b/backend/internal/server/api_contract_test.go
@@ -1434,6 +1434,10 @@ func (r *stubApiKeyRepo) ListKeysByGroupID(ctx context.Context, groupID int64) (
 	return nil, errors.New("not implemented")
 }
 
+func (r *stubApiKeyRepo) IncrementQuotaUsed(ctx context.Context, id int64, amount float64) (float64, error) {
+	return 0, errors.New("not implemented")
+}
+
 type stubUsageLogRepo struct {
 	userLogs map[int64][]service.UsageLog
 }
diff --git a/backend/internal/service/api_key_service.go b/backend/internal/service/api_key_service.go
index 38a5760c..b27682f3 100644
--- a/backend/internal/service/api_key_service.go
+++ b/backend/internal/service/api_key_service.go
@@ -17,15 +17,15 @@ import (
 )
 
 var (
-	ErrAPIKeyNotFound       = infraerrors.NotFound("API_KEY_NOT_FOUND", "api key not found")
-	ErrGroupNotAllowed      = infraerrors.Forbidden("GROUP_NOT_ALLOWED", "user is not allowed to bind this group")
-	ErrAPIKeyExists         = infraerrors.Conflict("API_KEY_EXISTS", "api key already exists")
-	ErrAPIKeyTooShort       = infraerrors.BadRequest("API_KEY_TOO_SHORT", "api key must be at least 16 characters")
-	ErrAPIKeyInvalidChars   = infraerrors.BadRequest("API_KEY_INVALID_CHARS", "api key can only contain letters, numbers, underscores, and hyphens")
-	ErrAPIKeyRateLimited    = infraerrors.TooManyRequests("API_KEY_RATE_LIMITED", "too many failed attempts, please try again later")
-	ErrInvalidIPPattern     = infraerrors.BadRequest("INVALID_IP_PATTERN", "invalid IP or CIDR pattern")
+	ErrAPIKeyNotFound     = infraerrors.NotFound("API_KEY_NOT_FOUND", "api key not found")
+	ErrGroupNotAllowed    = infraerrors.Forbidden("GROUP_NOT_ALLOWED", "user is not allowed to bind this group")
+	ErrAPIKeyExists       = infraerrors.Conflict("API_KEY_EXISTS", "api key already exists")
+	ErrAPIKeyTooShort     = infraerrors.BadRequest("API_KEY_TOO_SHORT", "api key must be at least 16 characters")
+	ErrAPIKeyInvalidChars = infraerrors.BadRequest("API_KEY_INVALID_CHARS", "api key can only contain letters, numbers, underscores, and hyphens")
+	ErrAPIKeyRateLimited  = infraerrors.TooManyRequests("API_KEY_RATE_LIMITED", "too many failed attempts, please try again later")
+	ErrInvalidIPPattern   = infraerrors.BadRequest("INVALID_IP_PATTERN", "invalid IP or CIDR pattern")
 	// ErrAPIKeyExpired        = infraerrors.Forbidden("API_KEY_EXPIRED", "api key has expired")
-	ErrAPIKeyExpired        = infraerrors.Forbidden("API_KEY_EXPIRED", "api key 已过期")
+	ErrAPIKeyExpired = infraerrors.Forbidden("API_KEY_EXPIRED", "api key 已过期")
 	// ErrAPIKeyQuotaExhausted = infraerrors.TooManyRequests("API_KEY_QUOTA_EXHAUSTED", "api key quota exhausted")
 	ErrAPIKeyQuotaExhausted = infraerrors.TooManyRequests("API_KEY_QUOTA_EXHAUSTED", "api key 额度已用完")
 )
@@ -94,7 +94,7 @@ type CreateAPIKeyRequest struct {
 	IPBlacklist []string `json:"ip_blacklist"` // IP 黑名单
 
 	// Quota fields
-	Quota         float64 `json:"quota"`          // Quota limit in USD (0 = unlimited)
+	Quota         float64 `json:"quota"`           // Quota limit in USD (0 = unlimited)
 	ExpiresInDays *int    `json:"expires_in_days"` // Days until expiry (nil = never expires)
 }
 
@@ -107,10 +107,10 @@ type UpdateAPIKeyRequest struct {
 	IPBlacklist []string `json:"ip_blacklist"` // IP 黑名单（空数组清空）
 
 	// Quota fields
-	Quota           *float64   `json:"quota"`          // Quota limit in USD (nil = no change, 0 = unlimited)
-	ExpiresAt       *time.Time `json:"expires_at"`     // Expiration time (nil = no change)
-	ClearExpiration bool       `json:"-"`              // Clear expiration (internal use)
-	ResetQuota      *bool      `json:"reset_quota"`    // Reset quota_used to 0
+	Quota           *float64   `json:"quota"`       // Quota limit in USD (nil = no change, 0 = unlimited)
+	ExpiresAt       *time.Time `json:"expires_at"`  // Expiration time (nil = no change)
+	ClearExpiration bool       `json:"-"`           // Clear expiration (internal use)
+	ResetQuota      *bool      `json:"reset_quota"` // Reset quota_used to 0
 }
 
 // APIKeyService API Key服务