API Gateway

• A API Gateway is a single point access for front-end applications or other internal subsystems
• Composes all the APIs of the internal services into a single API (API composition)
• It proxies requests to the appropriate internal service

flowchart LR

A[Client]
B[API Gateway]
C[Frontend Service]
D[Users Service]
E[Video Service]
F[Comments Service]

A --> B
B --> C
B --> D
B --> E
B --> F

Features

1. API composition
2. Request routing
   • The gateway aggregates information from multiple internal endpoints
   • This concept is similar to BFF (Back For Front)
3. Authentication & Authorization
4. Rate limits
   • Request throttling
   • To block DoS attacks
5. Caching
   • Caches static content
   • Caches stateless responses
6. Monitoring and Alerting
   • The monitoring of the API gateway may point out issues on the overall system working
   • E.g., sudden throughput drop, high latency, etc
7. Protocol Translation
   • E.g., Convert REST+JSON to gRPC+protobuf
   • E.g., Convert SOAP+XML to REST+JSON
8. Versioning
   • According to a header, may redirect the request to different versions of the internal API

Anti-Pattern

1. Should NOT contain business logic
2. Should NOT be a single point of failure (have multiple instances behind a LB)
3. Changes to the API Gateway must be very cautious (adopt blue/green or similar deployment strategies)

Implementations

• Open Source
• Zuul: created by netflix
• Cloud based
• AWS API Gateway
• GCP API Gateway
• Azure API Management