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middleware-design

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Designing robust middleware chains (Auth, Rate Limiting, Logging).

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Source SKILL.md: https://github.com/majiayu000/claude-skill-registry/blob/HEAD/skills/development/architecture-andreibesleaga-gabbe-5/SKILL.md

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middleware-design Skill

This skill guides the creation of the request processing pipeline ("The Onion Architecture").

1. The Standard Pipeline (Order Matters)

  1. Request ID: Generate trace_id immediately. (Before logs).
  2. CORS: Allow/Block origins. (Before processing).
  3. Body Parser: JSON/Form parsing. (Limit size to prevent DoS).
  4. Rate Limiter: Token Bucket algorithm. (Stop abuse cheaply).
  5. Authentication: Verify JWT/Session. (Who is it?).
  6. Authorization: Check Roles/Scopes. (Can they do it?).
  7. Validation: Zod/Pydantic schema check. (Is input valid?).
  8. Controller: Business Logic.
  9. Error Handler: Catch exceptions, format JSON, scrub sensitive data.

2. Implementation Rules

  • Fail Fast: If Rate Limit check fails, return 429 immediately. Do not parse body.
  • Context Passing: Pass user and trace_id via Context (Go/React) or Request Object (Express/FastAPI).
  • No Business Logic: Middleware should be generic. Don't query SELECT * FROM orders in middleware.

3. Specific Patterns

Rate Limiting

  • Global: 1000 req/min/IP.
  • Route-Specific: Login = 5 req/min/IP.
  • Storage: Use Redis. Local memory rate limiting doesn't work in clustered apps.

Response Interceptors

  • Use for consistent response formatting.
  • data: { ... }, meta: { trace_id: ... }.

Error Handling Middleware

  • NEVER return raw stack trace to client in Production.
  • ALWAYS log raw stack trace to logger.