What is API Gateway?

Definition

An API Gateway is a management tool that sits between clients and a collection of backend services. It acts as a reverse proxy, accepting all API calls, routing them to the appropriate service, and returning the results.

API Gateways are essential in microservices architectures, where they provide a unified entry point instead of exposing dozens of individual service endpoints.

What an API Gateway Does

• Request routing: Routes incoming requests to the correct backend service.
• Authentication: Validates tokens, API keys, or certificates before forwarding requests.
• Rate limiting: Protects backend services from excessive traffic.
• Load balancing: Distributes requests across multiple service instances.
• Response caching: Caches responses to reduce backend load.
• Request/response transformation: Modifies headers, payloads, or protocols.
• SSL termination: Handles HTTPS encryption/decryption.
• Monitoring: Collects metrics, logs, and traces for observability.

Popular API Gateways

• Kong: Open-source, high-performance gateway built on Nginx. Supports plugins for auth, rate limiting, and more.
• AWS API Gateway: Fully managed gateway for AWS with Lambda integration.
• Traefik: Cloud-native gateway with automatic service discovery and Let's Encrypt support.
• NGINX: Widely used as a reverse proxy and API gateway.
• Envoy: High-performance proxy designed for microservices (used in service meshes like Istio).

Frequently Asked Questions

Do I need an API Gateway?

For a single backend service, a simple reverse proxy (Nginx, Caddy) is usually sufficient. API Gateways become valuable with microservices architectures where you need centralized authentication, rate limiting, and routing across multiple services.