Frontend to Backend API Integration Sequence diagram illustrates a two-phase authentication and data retrieval flow using AWS API Gateway, Authentication Service, and User Service. Phase 1 captures JWT-based authentication where the Frontend submits credentials to API Gateway, which routes to the Authentication Service for token generation and client-side storage. Phase 2 demonstrates authenticated data retrieval: the Frontend includes the JWT in subsequent requests, API Gateway validates the token before routing to User Service, which queries the Database and returns results. This architecture enforces least-privilege access and separation of concerns across Frontend, Backend, Services, and Database layers. Fork this diagram on Diagrams.so to customize authentication mechanisms, add rate limiting, or integrate AWS Cognito for managed identity. The sequence pattern is ideal for microservices where stateless JWT validation reduces backend coupling and improves scalability.