When designing APIs with Express, prioritize proper REST principles and HTTP semantics over convenience. This ensures your API is predictable, standards-compliant, and maintainable: 1. **Use appropriate HTTP verbs** for different operations: - GET for retrieval - POST for creation - PUT for complete entity updates - PATCH for partial updates - DELETE for removal ```javascript // Implement both PUT and PATCH for different update scenarios router.put('/:id', controller.replaceEntity.bind(controller)); // Full entity replacement router.patch('/:id', controller.updateFields.bind(controller)); // Partial update ``` 2. **Handle HTTP headers correctly**: - Respect existing Content-Type headers before applying defaults - Follow established patterns for setting headers (use `res.type()` where appropriate) - Handle Link headers according to RFC specifications - Process Accept headers intelligently, considering priorities 3. **Follow consistent response patterns**: - Use `res.status()` with appropriate status codes (200 OK, 201 Created, 204 No Content) - For error responses, use semantic status codes (400 Bad Request, 404 Not Found) - Use `res.sendStatus()` for simple status-only responses Remember that proper HTTP semantics help clients understand your API intuitively without requiring extensive documentation for basic operations.