API Gateway: Role and Core Functions in Microservices

API Gateway

Core Functions

Function	Description
Routing	Forward requests to microservices
Auth	Centralized JWT/API Key validation
Rate Limiting	Traffic control, DDoS protection
SSL Termination	Handle HTTPS at edge
Request Transform	Format conversion, field filtering
Load Balancing	Distribute traffic across instances
Caching	Cache frequent responses
Observability	Centralized logging/tracing/metrics

Common Implementations

• Kong: Open-source, Nginx-based, rich plugins
• AWS API Gateway: Serverless-friendly
• Nginx / Traefik: Lightweight, self-hosted
• Envoy: High-performance, powers Istio

BFF (Backend for Frontend)

Different clients get dedicated BFFs that aggregate specific microservice data—more flexible than a single shared gateway.

Gotchas

• Gateway is a single point of failure—deploy with HA (multiple instances + health checks)
• Keep Gateway as a thin layer; avoid business logic here