Cloud-Native Patterns

Twelve-Factor App

1. Codebase: One codebase, many deploys
2. Dependencies: Explicitly declare and isolate
3. Config: Store in environment
4. Backing Services: Treat as attached resources
5. Build, Release, Run: Strictly separate stages
6. Processes: Execute as stateless processes
7. Port Binding: Export services via port
8. Concurrency: Scale out via process model
9. Disposability: Fast startup and graceful shutdown
10. Dev/Prod Parity: Keep environments similar
11. Logs: Treat as event streams
12. Admin Processes: Run as one-off processes

Resilience Patterns

Circuit Breaker

Prevent cascading failures by failing fast.

class CircuitBreaker {
  private failures = 0;
  private lastFailure?: Date;

  async call<T>(fn: () => Promise<T>): Promise<T> {
    if (this.isOpen()) {
      throw new Error('Circuit is open');
    }
    try {
      const result = await fn();
      this.reset();
      return result;
    } catch (error) {
      this.recordFailure();
      throw error;
    }
  }
}

Retry with Backoff

async function withRetry<T>(
  fn: () => Promise<T>,
  maxRetries = 3
): Promise<T> {
  for (let i = 0; i < maxRetries; i++) {
    try {
      return await fn();
    } catch (error) {
      if (i === maxRetries - 1) throw error;
      await sleep(Math.pow(2, i) * 1000); // Exponential backoff
    }
  }
}

Bulkhead

Isolate failures to prevent system-wide impact.

Service Communication

Synchronous

• REST/HTTP
• gRPC

Asynchronous

• Message queues (RabbitMQ, SQS)
• Event streaming (Kafka)

Health Checks

app.get('/health', (req, res) => {
  res.json({ status: 'healthy' });
});

app.get('/ready', async (req, res) => {
  const dbHealthy = await checkDatabase();
  const cacheHealthy = await checkCache();

  if (dbHealthy && cacheHealthy) {
    res.json({ status: 'ready' });
  } else {
    res.status(503).json({ status: 'not ready' });
  }
});

Container Best Practices

• One process per container
• Use multi-stage builds
• Run as non-root user
• Use health checks
• Keep images small