diff --git a/apps/carrier-connector/internal/tenant/interface.go b/apps/carrier-connector/internal/tenant/interface.go
new file mode 100644
index 0000000..53a17b4
--- /dev/null
+++ b/apps/carrier-connector/internal/tenant/interface.go
@@ -0,0 +1,164 @@
+package tenant
+
+import (
+	"context"
+	"time"
+)
+
+// Repository defines the interface for tenant data operations
+type Repository interface {
+	// Tenant operations
+	CreateTenant(ctx context.Context, tenant *Tenant) error
+	GetTenant(ctx context.Context, id string) (*Tenant, error)
+	GetTenantByDomain(ctx context.Context, domain string) (*Tenant, error)
+	UpdateTenant(ctx context.Context, tenant *Tenant) error
+	DeleteTenant(ctx context.Context, id string) error
+	ListTenants(ctx context.Context, filter *TenantFilter) ([]*Tenant, error)
+	CountTenants(ctx context.Context, filter *TenantFilter) (int, error)
+
+	// Tenant user operations
+	CreateTenantUser(ctx context.Context, user *TenantUser) error
+	GetTenantUser(ctx context.Context, tenantID, userID string) (*TenantUser, error)
+	UpdateTenantUser(ctx context.Context, user *TenantUser) error
+	DeleteTenantUser(ctx context.Context, tenantID, userID string) error
+	ListTenantUsers(ctx context.Context, filter *TenantUserFilter) ([]*TenantUser, error)
+	CountTenantUsers(ctx context.Context, filter *TenantUserFilter) (int, error)
+
+	// API key operations
+	CreateAPIKey(ctx context.Context, apiKey *TenantAPIKey) error
+	GetAPIKey(ctx context.Context, id string) (*TenantAPIKey, error)
+	GetAPIKeyByHash(ctx context.Context, keyHash string) (*TenantAPIKey, error)
+	UpdateAPIKey(ctx context.Context, apiKey *TenantAPIKey) error
+	DeleteAPIKey(ctx context.Context, id string) error
+	ListAPIKeys(ctx context.Context, tenantID string) ([]*TenantAPIKey, error)
+
+	// Usage tracking operations
+	CreateUsage(ctx context.Context, usage *TenantUsage) error
+	GetUsage(ctx context.Context, tenantID, resourceType string) (*TenantUsage, error)
+	UpdateUsage(ctx context.Context, usage *TenantUsage) error
+	ListUsage(ctx context.Context, filter *TenantUsageFilter) ([]*TenantUsage, error)
+	GetUsageStats(ctx context.Context, tenantID string) (*TenantUsageStats, error)
+
+	// Configuration operations
+	GetConfig(ctx context.Context, tenantID string) (*TenantConfig, error)
+	UpdateConfig(ctx context.Context, config *TenantConfig) error
+
+	// Event operations
+	CreateEvent(ctx context.Context, event *TenantEvent) error
+	ListEvents(ctx context.Context, tenantID string, limit int) ([]*TenantEvent, error)
+}
+
+// Service defines the interface for tenant business operations
+type Service interface {
+	// Tenant management
+	CreateTenant(ctx context.Context, req *CreateTenantRequest) (*Tenant, error)
+	GetTenant(ctx context.Context, id string) (*Tenant, error)
+	GetTenantByDomain(ctx context.Context, domain string) (*Tenant, error)
+	UpdateTenant(ctx context.Context, id string, req *UpdateTenantRequest) (*Tenant, error)
+	DeleteTenant(ctx context.Context, id string) error
+	ListTenants(ctx context.Context, filter *TenantFilter) ([]*Tenant, error)
+
+	// User management
+	AddUserToTenant(ctx context.Context, req *CreateTenantUserRequest) (*TenantUser, error)
+	GetTenantUser(ctx context.Context, tenantID, userID string) (*TenantUser, error)
+	UpdateTenantUser(ctx context.Context, tenantID, userID string, req *UpdateTenantUserRequest) (*TenantUser, error)
+	RemoveUserFromTenant(ctx context.Context, tenantID, userID string) error
+	ListTenantUsers(ctx context.Context, filter *TenantUserFilter) ([]*TenantUser, error)
+
+	// API key management
+	CreateAPIKey(ctx context.Context, tenantID string, req *CreateAPIKeyRequest) (*TenantAPIKey, string, error)
+	GetAPIKey(ctx context.Context, id string) (*TenantAPIKey, error)
+	UpdateAPIKey(ctx context.Context, id string, req *UpdateAPIKeyRequest) (*TenantAPIKey, error)
+	DeleteAPIKey(ctx context.Context, id string) error
+	ListAPIKeys(ctx context.Context, tenantID string) ([]*TenantAPIKey, error)
+	ValidateAPIKey(ctx context.Context, key string) (*TenantAPIKey, error)
+
+	// Quota and usage management
+	CheckQuota(ctx context.Context, tenantID, resourceType string, count int) error
+	GetUsageStats(ctx context.Context, tenantID string) (*TenantUsageStats, error)
+	UpdateUsage(ctx context.Context, tenantID, resourceType string, count int) error
+	GetQuotaStatus(ctx context.Context, tenantID string) (map[string]QuotaStatus, error)
+
+	// Configuration management
+	GetTenantConfig(ctx context.Context, tenantID string) (*TenantConfig, error)
+	UpdateTenantConfig(ctx context.Context, tenantID string, config *TenantConfig) error
+	GetTenantSettings(ctx context.Context, tenantID string) (*TenantSettings, error)
+
+	// Authentication and authorization
+	ValidateTenantAccess(ctx context.Context, tenantID, userID string) (*TenantContext, error)
+	HasPermission(ctx context.Context, tenantID, userID string, permission string) (bool, error)
+	GetTenantContext(ctx context.Context, tenantID string) (*TenantContext, error)
+
+	// Analytics and monitoring
+	GetTenantMetrics(ctx context.Context, tenantID string) (*TenantMetrics, error)
+	GetTenantEvents(ctx context.Context, tenantID string, limit int) ([]*TenantEvent, error)
+	LogTenantEvent(ctx context.Context, event *TenantEvent) error
+}
+
+// Middleware defines the interface for tenant middleware
+type Middleware interface {
+	// Request middleware
+	ExtractTenantFromRequest(ctx context.Context, request interface{}) (*TenantContext, error)
+	ValidateTenantAccess(ctx context.Context, tenantCtx *TenantContext) error
+	InjectTenantContext(ctx context.Context, tenantCtx *TenantContext) context.Context
+
+	// Rate limiting
+	CheckRateLimit(ctx context.Context, tenantCtx *TenantContext, endpoint string) error
+	RecordAPIUsage(ctx context.Context, tenantCtx *TenantContext, endpoint string)
+
+	// Resource isolation
+	IsolateTenantData(ctx context.Context, tenantCtx *TenantContext) context.Context
+	ValidateResourceAccess(ctx context.Context, tenantCtx *TenantContext, resource string, resourceID string) error
+}
+
+// EventPublisher defines the interface for publishing tenant events
+type EventPublisher interface {
+	PublishTenantEvent(ctx context.Context, event *TenantEvent) error
+	PublishQuotaExceeded(ctx context.Context, tenantID, resourceType string) error
+	PublishTenantCreated(ctx context.Context, tenant *Tenant) error
+	PublishTenantDeleted(ctx context.Context, tenantID string) error
+}
+
+// RateLimiter defines the interface for tenant rate limiting
+type RateLimiter interface {
+	Allow(ctx context.Context, tenantID, key string) bool
+	GetRemaining(ctx context.Context, tenantID, key string) int
+	GetResetTime(ctx context.Context, tenantID, key string) time.Time
+	Reset(ctx context.Context, tenantID, key string)
+}
+
+// ResourceManager defines the interface for managing tenant resources
+type ResourceManager interface {
+	AllocateResource(ctx context.Context, tenantID, resourceType string, count int) error
+	DeallocateResource(ctx context.Context, tenantID, resourceType string, count int) error
+	GetResourceUsage(ctx context.Context, tenantID, resourceType string) (*ResourceUsage, error)
+	GetResourceQuota(ctx context.Context, tenantID, resourceType string) (*ResourceQuota, error)
+	SetResourceQuota(ctx context.Context, tenantID, resourceType string, quota *ResourceQuota) error
+}
+
+// ConfigManager defines the interface for managing tenant configuration
+type ConfigManager interface {
+	GetConfig(ctx context.Context, tenantID string) (*TenantConfig, error)
+	SetConfig(ctx context.Context, tenantID string, config *TenantConfig) error
+	UpdateConfig(ctx context.Context, tenantID string, updates map[string]interface{}) error
+	GetSetting(ctx context.Context, tenantID, key string) (interface{}, error)
+	SetSetting(ctx context.Context, tenantID, key string, value interface{}) error
+	DeleteSetting(ctx context.Context, tenantID, key string) error
+}
+
+// AuditLogger defines the interface for tenant audit logging
+type AuditLogger interface {
+	LogTenantAction(ctx context.Context, tenantID, userID, action string, details map[string]interface{}) error
+	LogAPIAccess(ctx context.Context, tenantID, userID, apiKey, endpoint, method string) error
+	LogResourceAccess(ctx context.Context, tenantID, userID, resource, resourceID, action string) error
+	LogQuotaViolation(ctx context.Context, tenantID, resourceType string, usage, limit int) error
+}
+
+// MetricsCollector defines the interface for collecting tenant metrics
+type MetricsCollector interface {
+	RecordTenantMetric(ctx context.Context, tenantID, metric string, value float64, tags map[string]string) error
+	RecordAPIRequest(ctx context.Context, tenantID, endpoint, method, statusCode string, duration time.Duration) error
+	RecordResourceUsage(ctx context.Context, tenantID, resourceType string, count int) error
+	RecordUserActivity(ctx context.Context, tenantID, userID, activity string) error
+	GetTenantMetrics(ctx context.Context, tenantID string, timeRange string) (map[string]float64, error)
+}