# API Design ## Decision Tree: API Architecture Style ``` What API architecture should we use? ├─ REST (RESTful API) [weight: 8] [priority: high] [risk: low] [recommended] │ ├─ Design Approach │ │ ├─ Resource-based URLs [recommended] → /users, /posts/{id} │ │ ├─ RPC-style → /getUser, /createPost │ │ └─ Hypermedia (HATEOAS) → Self-describing API │ ├─ Response Format │ │ ├─ JSON [recommended] → Standard for web │ │ ├─ XML → Legacy systems │ │ └─ MessagePack → Binary, efficient │ ├─ Versioning Strategy │ │ ├─ URL versioning [recommended] → /v1/users, /v2/users │ │ ├─ Header versioning → Accept: application/vnd.api.v1+json │ │ └─ Query parameter → /users?version=1 │ ├─ Documentation │ │ ├─ OpenAPI/Swagger [recommended] → Interactive docs │ │ ├─ API Blueprint → Markdown-based │ │ └─ Postman Collections → Shareable examples │ └─ Best for │ ├─ Web applications → Most common │ ├─ Mobile apps → Wide client support │ ├─ Public APIs → Well-understood │ └─ CRUD operations → Natural fit │ ├─ GraphQL [weight: 7] [priority: medium] [risk: medium] │ ├─ Implementation │ │ ├─ Apollo Server [weight: 9] [recommended] │ │ │ ├─ Features: Full-featured, great tooling │ │ │ ├─ Caching: Built-in Apollo Client │ │ │ └─ Subscriptions: Real-time support │ │ ├─ Relay → Facebook's approach, complex │ │ └─ GraphQL Yoga → Lightweight, modern │ ├─ Schema Design │ │ ├─ Code-first [recommended] → TypeScript decorators │ │ ├─ Schema-first → SDL files │ │ └─ Auto-generated → From database │ ├─ Advantages │ │ ├─ Single endpoint → /graphql │ │ ├─ Client specifies data → No over-fetching │ │ ├─ Strong typing → Type safety │ │ └─ Introspection → Self-documenting │ ├─ Challenges │ │ ├─ Caching complexity → Non-standard HTTP caching │ │ ├─ N+1 query problem → Needs DataLoader │ │ ├─ File uploads → Requires special handling │ │ └─ Learning curve → Team must learn GraphQL │ └─ Best for │ ├─ Complex data requirements → Multiple related entities │ ├─ Mobile apps → Reduce bandwidth │ ├─ Multiple clients → Each gets what it needs │ └─ Rapid iteration → Schema evolution │ ├─ gRPC [weight: 6] [priority: low] [risk: medium] │ ├─ Protocol Buffers │ │ ├─ Define .proto files → Strongly typed schemas │ │ ├─ Code generation → Client/server stubs │ │ └─ Backward compatibility → Version-safe │ ├─ Communication Patterns │ │ ├─ Unary → Single request/response │ │ ├─ Server streaming → Multiple responses │ │ ├─ Client streaming → Multiple requests │ │ └─ Bidirectional streaming → Full duplex │ ├─ Advantages │ │ ├─ Performance → Binary protocol, HTTP/2 │ │ ├─ Type safety → Strong contracts │ │ ├─ Streaming → Native support │ │ └─ Code generation → Less boilerplate │ ├─ Challenges │ │ ├─ Browser support → Limited without proxy │ │ ├─ Debugging → Binary format harder to inspect │ │ ├─ Learning curve → Protobuf syntax │ │ └─ Tooling → Less mature than REST │ └─ Best for │ ├─ Microservices → Service-to-service │ ├─ Real-time systems → Low latency needed │ ├─ Mobile backends → Efficient binary │ └─ Polyglot systems → Multi-language support │ ├─ WebSocket [weight: 6] [priority: low] [risk: medium] │ ├─ Protocols │ │ ├─ Socket.io [recommended] → Easy, fallback support │ │ ├─ Native WebSocket → Standard, lightweight │ │ └─ Server-Sent Events → One-way, simpler │ ├─ Message Format │ │ ├─ JSON → Human-readable │ │ ├─ Protocol Buffers → Efficient binary │ │ └─ MessagePack → Compact JSON alternative │ └─ Best for │ ├─ Real-time apps → Chat, notifications │ ├─ Live updates → Stock tickers, sports scores │ ├─ Collaborative editing → Google Docs-style │ └─ Gaming → Low latency needed │ └─ Webhook [weight: 5] [priority: low] [risk: low] ├─ Event-driven → Server pushes to clients ├─ Retry Logic → Handle failures gracefully ├─ Security → HMAC signatures, IP whitelisting └─ Best for ├─ Integrations → Third-party services ├─ Async notifications → Payment confirmations └─ Event broadcasting → System events ``` ## Context API architecture choice depends on: - Client requirements (web, mobile, desktop) - Data complexity and relationships - Real-time needs - Team expertise - Performance requirements ## Recommendations **REST is recommended** for most applications because: - Universal understanding and support - Simple to implement and test - Great tooling and documentation - Works everywhere (browsers, mobile, servers) - Established patterns and best practices **Use GraphQL** if: - You have complex, nested data relationships - Multiple client types with different needs - You want to avoid versioning endpoints - Mobile bandwidth is a concern - Your team is willing to invest in learning **Use gRPC** if: - Building microservices (service-to-service) - Performance is critical - Strong typing is required - Browser access is not needed **Use WebSocket** if: - You need true real-time bidirectional communication - Low latency is critical - You're building chat, gaming, or live updates ## REST Best Practices ### URL Structure ``` ✅ Good: GET /api/users/{id} ❌ Bad: GET /api/getUser?id={id} ✅ Good: POST /api/users ❌ Bad: POST /api/createUser ✅ Good: GET /api/users/{id}/posts ❌ Bad: GET /api/posts?userId={id} ``` ### HTTP Methods - `GET` - Retrieve resource(s) - `POST` - Create new resource - `PUT` - Update entire resource - `PATCH` - Update partial resource - `DELETE` - Delete resource ### Status Codes - `200` - Success - `201` - Created - `204` - No Content (successful delete) - `400` - Bad Request (client error) - `401` - Unauthorized - `403` - Forbidden - `404` - Not Found - `500` - Server Error ## Implementation Checklist - [ ] Choose API style (REST/GraphQL/gRPC) - [ ] Design URL structure (REST) or schema (GraphQL) - [ ] Implement authentication (JWT, OAuth) - [ ] Add rate limiting - [ ] Set up CORS properly - [ ] Implement error handling - [ ] Add request validation - [ ] Write API documentation - [ ] Set up API versioning - [ ] Add monitoring/analytics - [ ] Implement caching strategy - [ ] Write integration tests - [ ] Create client SDK (optional)