API Design Patterns for Modern Applications

Build scalable, maintainable APIs with proven design patterns.

API Styles

REST: Resource-based, HTTP methods, stateless, widely adopted GraphQL: Query language, client-specified responses, single endpoint, efficient data fetching gRPC: High performance, protocol buffers, bidirectional streaming, microservices WebSocket: Real-time, bidirectional, persistent connections, live updates

REST Best Practices

Resources: Nouns not verbs (/users not /getUsers), plural names, hierarchical HTTP Methods: GET (read), POST (create), PUT (replace), PATCH (update), DELETE (remove) Status Codes: 200 (OK), 201 (created), 400 (bad request), 401 (unauthorized), 404 (not found), 500 (server error) Versioning: URL (/v1/users), header (Accept: application/vnd.api+json; version=1)

GraphQL Patterns

Schema Design: Strong typing, clear field names, avoid overfetching Resolvers: Efficient data loading, batching, caching, N+1 prevention Mutations: Clear naming, return modified objects, atomic operations Subscriptions: Real-time updates, WebSocket transport, selective events

API Security

Authentication: OAuth 2.0, JWT tokens, API keys, mutual TLS Authorization: RBAC, scope-based permissions, resource-level access Rate Limiting: Token bucket, fixed window, prevent abuse Input Validation: Schema validation, sanitization, type checking

Design Patterns

Pagination: Offset-based, cursor-based, limit/offset Filtering: Query parameters, field selection, search Sorting: Multiple fields, ascending/descending, default ordering Caching: ETag, Cache-Control, conditional requests

Error Handling

Consistent Format: Standard error objects, error codes, messages Detail Levels: User-friendly vs debugging information Validation Errors: Field-level errors, multiple errors Retry Logic: Idempotency keys, exponential backoff

Documentation

OpenAPI/Swagger: Auto-generated docs, interactive testing Examples: Request/response samples, common scenarios Changelog: Version history, breaking changes, migration guides

Performance

Compression: gzip, brotli Lazy Loading: On-demand data fetching Batch Operations: Reduce round trips CDN: Cache static responses globally

Versioning Strategies

URL Versioning: /v1/resource—simple, clear Header Versioning: Accept: application/vnd.api.v1+json—cleaner URLs Query Parameters: /resource?version=1—flexible

Testing

Unit tests for handlers, integration tests for endpoints, contract testing for consumers Load testing, security testing, monitoring

Best Practices

1. Design for clients, not implementation
2. Use consistent naming conventions
3. Return appropriate status codes
4. Implement proper error handling
5. Version from day one
6. Document thoroughly
7. Monitor usage patterns
8. Design for backwards compatibility

Bottom Line

Good API design requires thinking about usability, security, performance, and maintainability. Prioritize developer experience and consistency.