backend-development-patterns

Backend Development Patterns Skill

Overview

This skill provides comprehensive backend development patterns including API design, database architecture, authentication, and scalable backend systems.

When to Use This Skill

• Designing and implementing REST/GraphQL APIs
• Database schema design and optimization
• Backend service architecture
• Microservices patterns
• Data layer implementation

Core API Design Principles (Level 1 - Always Loaded)

REST API Best Practices

URL Structure:

✅ GOOD - Resource-oriented URLs
GET    /api/users           # List users
GET    /api/users/:id       # Get specific user
POST   /api/users           # Create user
PUT    /api/users/:id       # Update user (full replace)
PATCH  /api/users/:id       # Update user (partial)
DELETE /api/users/:id       # Delete user

# Nested resources
GET    /api/users/:id/orders      # Get user's orders
POST   /api/users/:id/orders      # Create order for user

❌ BAD - Verb-based URLs
GET    /api/getUser?id=123
POST   /api/createUser
POST   /api/updateUser
POST   /api/deleteUser

HTTP Status Codes:

// Success responses
200 OK              // Successful GET, PUT, PATCH, DELETE
201 Created         // Successful POST
204 No Content      // Successful DELETE (no response body)

// Client errors
400 Bad Request     // Invalid input data
401 Unauthorized    // Missing or invalid authentication
403 Forbidden       // Valid auth but insufficient permissions
404 Not Found       // Resource doesn't exist
409 Conflict        // Resource conflict (e.g., duplicate email)
422 Unprocessable   // Validation errors

// Server errors
500 Internal Error  // Unexpected server error
503 Service Unavail // Temporary unavailability

// Example usage
app.post('/api/users', async (req, res) => {
  try {
    const user = await userService.create(req.body);
    res.status(201).json(user); // 201 Created
  } catch (error) {
    if (error instanceof ValidationError) {
      res.status(422).json({ error: error.message }); // 422 Validation
    } else if (error instanceof ConflictError) {
      res.status(409).json({ error: error.message }); // 409 Conflict
    } else {
      res.status(500).json({ error: 'Internal server error' }); // 500
    }
  }
});