An API Gateway sits between clients (Mobile, Web) and services. It acts as a reverse proxy, accepting all API calls, aggregating the various services required to fulfill them, and returning the appropriate result.

When to Use

Microservices: Essential to hide the complexity of backend services (Service Discovery).
Cross-Cutting Concerns: Centralizing Authentication, SSL Termination, Rate Limiting, and Logging.
Protocol Translation: Converting HTTP (Client) to gRPC (Internal).

Core Functionality

Routing

GET /users -> User Service GET /orders -> Order Service

Aggregation (BFF - Backend for Frontend)

Combining results. One request to Gateway -> Calls User Service + Order Service -> Returns combined JSON.

Offloading

When to Use

Microservices: Essential to hide the complexity of backend services (Service Discovery).
Cross-Cutting Concerns: Centralizing Authentication, SSL Termination, Rate Limiting, and Logging.
Protocol Translation: Converting HTTP (Client) to gRPC (Internal).

Core Functionality

Routing

GET /users -> User Service GET /orders -> Order Service

Aggregation (BFF - Backend for Frontend)

Combining results. One request to Gateway -> Calls User Service + Order Service -> Returns combined JSON.

Error	Cause	Solution
`502 Bad Gateway`	Upstream service down or unreachable.	Check internal service health and firewall rules.
`504 Gateway Timeout`	Upstream taking too long.	Optimize service or increase timeout (carefully).

Api Gateway

When to Use

Core Functionality

Routing

Aggregation (BFF - Backend for Frontend)

Offloading

Api Gateway

When to Use

Core Functionality

Routing

Aggregation (BFF - Backend for Frontend)

Offloading

Common Patterns

Backend for Frontend (BFF)

Best Practices

Troubleshooting

References

Xurl

Acp Router

Coding Standards

Api Design

Mcp Server Patterns

Backend Patterns