API Gateway Design

When you're building a system with multiple microservices, letting clients communicate directly with each service creates many problems. Clients need to know about all services, handle different protocols, and deal with authentication multiple times. An API Gateway solves these problems by acting as a single entry point for all client requests.

Here's how an API Gateway helps:

Authentication & Authorization

Instead of implementing security in each microservice, the API Gateway handles it centrally. When a request comes in, the gateway first checks if the user is allowed to access the service. This means your microservices can focus on their core functionality rather than dealing with security.

Request Routing

The gateway knows where each service lives and forwards requests to the right place. If you move a service to a different server, you only need to update the gateway's routing configuration. Clients don't need to know or care about these changes.

Request/Response Transformation

Different clients (mobile apps, web browsers, IoT devices) might need data in different formats. The API Gateway can transform requests and responses to match what each client expects. For example, a mobile app might need a lightweight response while a web app needs more detailed data.

Rate Limiting

To protect your services from being overwhelmed, the gateway can limit how many requests each client can make. This prevents any single client from using too many resources and keeps your system stable.

Monitoring & Analytics

Since all requests go through the gateway, it's the perfect place to collect metrics about API usage. You can track things like response times, error rates, and popular endpoints without adding code to your services.

Best Practices:

Keep the gateway simple - avoid adding business logic
Use caching for frequently requested data
Implement circuit breakers to handle service failures gracefully
Monitor gateway performance closely
Plan for scaling - the gateway can become a bottleneck