Understanding Serverless

Serverless computing allows you to build and run applications without thinking about servers. The cloud provider manages infrastructure, scaling, and availability.

When to Use Serverless

Good Fit

• Variable or unpredictable workloads
• Event-driven processing
• APIs with inconsistent traffic
• Scheduled tasks and automation
• Rapid prototyping

Poor Fit

• Consistent high-throughput workloads
• Long-running processes (>15 minutes)
• Applications with specific hardware needs
• Very latency-sensitive applications

Architecture Patterns

API Backend

Client → API Gateway → Lambda → DynamoDB
                    ↘ Lambda → S3

Event Processing

S3 Upload → Lambda → Process → SQS → Lambda → Store
Kinesis Stream → Lambda → Transform → S3

Scheduled Tasks

EventBridge Rule (cron) → Lambda → Process
                       → Step Functions → Complex Workflow

Best Practices

Function Design

// Single responsibility
export async function handler(event) {
  // Parse event
  const order = parseOrderEvent(event);
  
  // Business logic
  const result = await processOrder(order);
  
  // Return response
  return {
    statusCode: 200,
    body: JSON.stringify(result)
  };
}

Cold Start Optimization

• Keep functions small and focused
• Minimize dependencies
• Use provisioned concurrency for critical paths
• Initialize connections outside handler

// Initialize outside handler
const db = new DynamoDB.DocumentClient();

export async function handler(event) {
  // db connection is reused
  return await db.get({...}).promise();
}

Error Handling

export async function handler(event) {
  try {
    return await processEvent(event);
  } catch (error) {
    console.error('Processing failed:', error);
    
    // Send to dead letter queue for retry
    await sqs.sendMessage({
      QueueUrl: process.env.DLQ_URL,
      MessageBody: JSON.stringify({ event, error: error.message })
    }).promise();
    
    throw error; // Let Lambda handle retry
  }
}

Observability

Structured Logging

console.log(JSON.stringify({
  level: 'INFO',
  message: 'Order processed',
  orderId: order.id,
  duration: Date.now() - start,
  requestId: context.awsRequestId
}));

Distributed Tracing

Use X-Ray or OpenTelemetry for end-to-end visibility across functions.

Cost Optimization

• Right-size memory allocation
• Optimize function duration
• Use reserved concurrency for predictable workloads
• Leverage Graviton processors (ARM)
• Monitor and alert on cost anomalies

Conclusion

Serverless enables rapid development and automatic scaling. Design for event-driven patterns and invest in observability for successful serverless applications.