Backend & API Development Skill

Build production-grade backend services with best practices in mind.

Your Backend Stack

Node.js/Express

• Framework: Express.js
• Runtime: Node.js 18+
• Language: JavaScript/TypeScript
• Database: PostgreSQL, MongoDB, or SQLite (context-dependent)
• Authentication: JWT or session-based

Python

• Web Framework: Flask or FastAPI
• Runtime: Python 3.9+
• Async Support: asyncio/aiohttp
• Database: Same as Node stack

Key Responsibilities

API Design

// RESTful conventions
GET    /api/resource      // List all
GET    /api/resource/:id  // Get one
POST   /api/resource      // Create
PUT    /api/resource/:id  // Update
DELETE /api/resource/:id  // Delete

Error Handling & Responses

// Consistent response format
{
  status: 'success' | 'error',
  data: {},           // For successful responses
  error: {            // For errors
    code: 'ERROR_CODE',
    message: 'Human readable',
    details: {}
  },
  timestamp: ISO8601
}

Middleware Pattern

// Standard Express middleware order:
1. Body parser
2. CORS / Security headers
3. Request logging
4. Authentication
5. Route handlers
6. Error handling (last)

Database Queries

• Use parameterized queries (prevent SQL injection)
• Implement connection pooling
• Add query logging for debugging
• Cache frequently accessed data

Authentication & Security

• JWT tokens with expiration
• Secure password hashing (bcrypt/argon2)
• CORS properly configured
• Rate limiting on sensitive endpoints
• Environment variables for secrets

Code Quality Standards

TypeScript Preference

// Type all endpoints
interface APIResponse<T> {
  status: 'success' | 'error'
  data?: T
  error?: APIError
}

// Handler typing
app.get('/api/users/:id', 
  async (req: Request, res: Response<APIResponse<User>>) => {
    // typed response
  }
)

Error Handling

// Global error handler (Express)
app.use((err, req, res, next) => {
  console.error(err)
  res.status(err.status || 500).json({
    status: 'error',
    error: {
      code: err.code || 'INTERNAL_ERROR',
      message: err.message
    }
  })
})

Logging Strategy

• INFO: API requests, cache hits/misses
• WARN: Deprecated endpoint usage, slow queries
• ERROR: Failed operations, exceptions
• DEBUG: Variable states, flow tracking

Performance Best Practices

• Connection pooling for databases
• Response caching with appropriate headers
• Pagination for large datasets
• Compression (gzip) for responses
• Database indexes on frequently queried fields
• Query optimization and explain plans

Testing

• Unit tests for business logic
• Integration tests for API endpoints
• Mock external services
• Test database fixtures
• Error case testing

Deployment Considerations

• Environment configuration (dev/staging/prod)
• Health check endpoints (/health)
• Graceful shutdown handling
• Database migration strategy
• Monitoring and alerting setup

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Output: Production-ready backend code with type safety, clear error handling, and scalable architecture.