API gateway patterns: routing, aggregation, authentication, and rate limiting

An API gateway is a single entry point for all client requests to your backend services. It handles cross-cutting concerns so your individual services can focus on business logic. A well-configured gateway simplifies client code and centralizes security and routing.

Routing is the gateway's primary function. It inspects incoming requests and forwards them to the appropriate backend service based on the URL path, headers, or other attributes. Routing configuration should be centralized and version-controlled. The gateway should handle service discovery integration.

Authentication at the gateway level validates tokens before requests reach your services. This centralizes authentication logic and ensures consistent enforcement. The gateway verifies JWTs, checks expiration, and optionally extracts user identity for downstream services via headers.

Rate limiting at the gateway protects all your services. The gateway tracks request counts per client and returns 429 responses when limits are exceeded. Centralized rate limiting is more efficient than implementing limits in each service. Configure different limits for different endpoints.

Request aggregation lets the gateway combine responses from multiple services into a single response. This reduces client-side network requests and simplifies client code. Be careful with aggregation it can couple the gateway too tightly to frontend needs and create a monolithic bottleneck.

Caching at the gateway improves response times and reduces backend load. Cache responses for GET endpoints with appropriate TTLs. The gateway can implement cache-aside or cache-through patterns. Invalidate cache entries when related data changes.

Canary and A/B testing support at the gateway lets you route traffic between service versions. Route a percentage of users to a new version based on user ID, cookie, or random sampling. This enables safe rollouts without client-side logic changes.

Choose your gateway implementation based on your infrastructure. Kong and Tyk are standalone gateways. AWS API Gateway integrates with the AWS ecosystem. NGINX can function as a lightweight gateway. A service mesh with Envoy or Istio provides gateway capabilities at the infrastructure layer.

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Rizwan Saleem | https://rizwansaleem.co