API Gateway Design Patterns

An API Gateway is a critical component in modern software architecture, especially for microservices and cloud-based applications. It acts as a single entry point for client requests and provides various features that simplify, secure, and optimize communication between clients and backend services.


Key Usages of an API Gateway

1. Request Routing:

  1. I. Directs incoming API requests to the appropriate backend service.
  2. II. Often includes path-based or host-based routing.
Example: /users routes to the User Service, /orders to the Order Service.

2. API Composition:

  1. I. Aggregates responses from multiple backend services and returns a unified response.
  2. II. Useful in microservices, where one request may require data from multiple services.

3. Authentication and Authorization:

  1. I. Acts as a gatekeeper by validating tokens (e.g., JWT, OAuth2).
  2. II. Enforces role-based access controls before forwarding requests.

4. Rate Limiting & Throttling:

  1. I. Prevents abuse by limiting how often clients can call APIs.
  2. II. Helps protect backend services from overload.
Example: 1000 requests per minute per user.

5. Caching:

  1. I. Stores frequently requested responses to reduce backend load and improve performance.
  2. II. Can be time-based or content-based.

6. Load Balancing:

  1. I. Distributes incoming traffic across multiple instances of a service.
  2. II. Improves reliability and performance.

7. Logging and Monitoring

  1. I. Tracks API usage, errors, and performance.
Feeds logs to monitoring tools (e.g., ELK Stack, Prometheus, Datadog).

8. Transformation and Mediation

  1. I. Modifies requests or responses (e.g., headers, body format).
  2. II. Helps adapt legacy APIs to modern clients.
Example: Convert XML response from a legacy service to JSON.

9. Security Filtering

  1. I. Blocks malicious requests using IP filtering, WAF (Web Application Firewall), or DDoS protection.
  2. II. Can inspect traffic for known attack signatures.

10. Versioning and Routing by Version

  1. I. Routes traffic based on API version in the path or header.
  2. II. Enables smooth transitions between API versions.
Example: /v1/orders → legacy system, /v2/orders → new microservice