backendlisted

# Backend Development Skill ## Before Building — Clarify: 1. **Framework/Language**: Node.js (Express/Fastify/Hono), Python (FastAPI/Django), Go, Java Spring? 2. **Database**: Relational (PostgreSQL/MySQL) or NoSQL (MongoDB/Redis)? 3. **Auth method**: JWT, sessions, OAuth, API keys? 4. **Deployment target**: Serverless, containers, VPS? 5. **Scale expectations**: Requests/sec, data volume? ## API Design Principles ### REST Best Practices - Use nouns for resources, verbs for HTTP methods - `GET /users/:id` not `GET /getUser` - Consistent response envelope: ```json { "data": {}, "error": null, "meta": { "page": 1, "total": 100 } } ``` - Use correct HTTP status codes (200, 201, 400, 401, 403, 404, 422, 500) - Version your API: `/api/v1/...` ### Request Validation - Validate and sanitize ALL inputs before processing - Return descriptive 422 errors with field-level messages - Use Zod (TS), Pydantic (Python), or class-validator ## Database Patterns ### Schema Design - Use UUIDs over sequential IDs for public-facing IDs - Always include `created_at`, `updated_at` timestamps - Index foreign keys and frequently queried columns - Soft deletes with `deleted_at` when data history matters ### Query Optimization - Avoid N+1 queries — use JOINs or eager loading - Use `EXPLAIN ANALYZE` to debug slow queries - Paginate all list endpoints (cursor-based for large datasets) - Cache expensive queries with Redis (TTL based on data freshness) ## Authentication & Sessions - Hash passwo