Building Scalable APIs with Node.js

Node.js can handle serious scale when done right. Here's what I've learned.

Foundation

Project Structure

Keep it organized:

src/
  controllers/
  services/
  repositories/
  middleware/
  utils/
  routes/

Dependency Injection

Makes testing and scaling easier:

class UserService {
  constructor(userRepository, cacheService) {
    this.userRepo = userRepository;
    this.cache = cacheService;
  }
}

Performance Patterns

1. Caching Strategy

Multi-level caching:

• Memory cache for hot data
• Redis for distributed cache
• Database as source of truth

  2. Connection Pooling

  Always pool database connections:

  const pool = new Pool({

max: 20, idleTimeoutMillis: 30000, connectionTimeoutMillis: 2000, });

3. Rate Limiting

Protect your API:

const limiter = rateLimit({
  windowMs: 15 * 60 * 1000,
  max: 100,
  standardHeaders: true,
});

Monitoring

What to track:

• Response times (p50, p95, p99)
• Error rates
• Active connections
• Memory usage

  Deployment

  - Use cluster mode for multi-core

• Container orchestration (K8s)
• Auto-scaling based on metrics

  Scale is a journey, not a destination.