Backend API

Design and implement RESTful API endpoints following REST principles, consistent naming conventions, versioning strategies, and proper HTTP methods. Use this skill when creating or modifying API route handlers in files like routes.js, routes.ts, api.py, routes.rb, controllers/*.js, controllers/*.ts, api/*.js, or any backend files that define HTTP endpoints and handle requests/responses. Use this when implementing CRUD operations with appropriate HTTP methods (GET for retrieving data, POST for creating new resources, PUT/PATCH for updating existing resources, DELETE for removing resources), designing RESTful URL structures with plural resource nouns like /users, /products, or /orders that follow REST conventions, setting up API versioning in URL paths like /v1/users or /api/v2/products or via headers for backward compatibility, defining query parameters for filtering collections (?status=active), sorting data (?sort=createdAt:desc), pagination (?page=2&limit=20), and search functionality (?q=search+term), configuring and returning appropriate HTTP status codes including 200 OK for successful GET requests, 201 Created for successful POST requests, 400 Bad Request for client errors and invalid input, 404 Not Found when resources don't exist, and 500 Internal Server Error for server-side errors, working with nested resource endpoints representing relationships like /users/:id/posts or /organizations/:id/members while limiting nesting depth to 2-3 levels maximum for URL readability and maintainability, implementing rate limiting mechanisms to prevent API abuse and DoS attacks and tracking API usage metrics for monitoring and analytics, creating middleware functions that process API requests or responses for cross-cutting concerns like authentication, logging, CORS handling, request validation, or response transformation, ensuring consistent lowercase hyphenated or underscored endpoint naming throughout the API (e.g., /api/user-profiles or /api/user_profiles, not mixed styles), and including rate limit information in response headers like X-RateLimit-Limit, X-RateLimit-Remaining, and X-RateLimit-Reset to inform clients of their quota status.