Architecture

API Gateway

A central entry point (reverse proxy) that receives, routes, secures and monitors all incoming API requests – the gateway to your microservices.

An API gateway is an essential building block of modern microservice architectures. It acts as the single entry point for all client requests and handles cross-cutting concerns such as authentication, rate limiting, logging and routing. Without an API gateway, every microservice would have to implement these tasks – a maintenance nightmare. With an API gateway the architecture is cleaner, more secure and easier to manage.

What is API Gateway?

An API gateway is a server that acts as a reverse proxy between clients (browsers, mobile apps, partner systems) and backend services. It receives all incoming API requests, forwards them to the appropriate service and returns the response to the client. It handles central tasks: authentication and authorization (e.g. JWT validation), rate limiting to prevent overload, request/response transformation, caching of frequent requests, load balancing across multiple service instances, API versioning and comprehensive monitoring with metrics and logging. Well-known implementations include Kong, AWS API Gateway, Nginx, Traefik and Apigee.

How does API Gateway work?

When a client sends an API request, it first hits the API gateway. The gateway checks authentication (e.g. API key or OAuth token). Then it checks the rate limit – if the client has exhausted its quota, the request is rejected with HTTP 429. For valid requests the gateway routes by URL path and HTTP method to the right backend service. Optionally it transforms the request (e.g. add headers, convert payload). The service response also passes through the gateway, may be cached and gets additional headers (CORS, security).

Practical Examples

An e-commerce company uses Kong as an API gateway to route and secure requests to 30+ microservices (products, orders, payments).

A fintech startup uses AWS API Gateway to expose its banking API to partners – with API keys, rate limiting and automatic scaling.

A media platform uses an API gateway to run different API versions (v1, v2, v3) in parallel and support legacy clients.

A healthcare company uses Traefik as gateway for its Kubernetes-based microservice architecture with automatic service discovery.

An industrial company aggregates data from several IoT services via an API gateway into a single response (Backend for Frontend pattern).

Typical Use Cases

Microservice architecture: Central routing, security and monitoring for all service-to-service and client-to-service communication

API monetization: Access control with API keys, usage tracking and billing data for partners and customers

Backend for Frontend (BFF): Different API endpoints for web, mobile and IoT clients with optimized payloads

Legacy integration: Modernization by putting a gateway in front that transforms old APIs and serves new clients

Multi-cloud strategy: Single API entry point regardless of whether services run on AWS, Azure or on-premise

Advantages and Disadvantages

Advantages

Centralized security: Authentication, authorization and encryption in one place instead of in every service
Reduced complexity: Clients talk to one endpoint instead of dozens of microservices
Scalability: Rate limiting, caching and load balancing protect backend services from overload
Observability: Central logging and monitoring of all API calls for fast troubleshooting
Flexibility: API versioning and request transformation enable evolution without breaking changes

Disadvantages

Single point of failure: If the gateway goes down, all services behind it are unreachable (mitigation: high availability)
Extra latency: Every request goes through an additional network hop, slightly increasing response time
Configuration complexity: Routing rules, policies and transformations can become hard to manage with many services
Vendor lock-in with cloud-native gateways like AWS API Gateway or Azure API Management

Frequently Asked Questions about API Gateway

What is the difference between an API gateway and a load balancer?

A load balancer distributes incoming traffic evenly across multiple instances of the same service (Layer 4/7). An API gateway adds intelligent routing to different services, authentication, rate limiting, request transformation, API versioning and monitoring. In practice both are often combined: the API gateway routes to the right service, the load balancer distributes within that service.

Do I need an API gateway for my project?

If you only have a single monolithic backend, a simple reverse proxy (Nginx) is often enough. As soon as you run multiple services, expose APIs to external partners or want to manage cross-cutting concerns like authentication and rate limiting centrally, an API gateway is the right choice.

Which API gateway fits my stack?

For Kubernetes, Kong, Traefik or Istio Ingress Gateway work well. For AWS-native architectures, AWS API Gateway. For on-premise with maximum control, Kong (open source) or Nginx Plus are proven. Key criteria are performance, plugin ecosystem, community support and integrations.

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