What is Serverless?

Serverless computing allows you to build and run applications without thinking about servers. AWS Lambda automatically runs your code in response to events, managing the compute resources for you. You pay only for the compute time you consume — there's no charge when your code isn't running.

This represents a fundamental shift in how we think about compute. Instead of provisioning servers and managing their lifecycle, you focus purely on your business logic. AWS handles everything else: the operating system, capacity, scaling, fault tolerance, and infrastructure management.

When to Use Lambda

Lambda excels at event-driven workloads: processing uploads to S3, handling API requests, responding to database changes, processing streams, running scheduled jobs. If your workload is bursty, unpredictable, or has periods of zero traffic, Lambda's pay-per-invocation model can dramatically reduce costs.

Lambda Basics

A Lambda function consists of your code, a runtime (Node.js, Python, Java, Go, etc.), and configuration that specifies memory, timeout, and permissions. When an event triggers your function, Lambda spins up an execution environment, runs your code, and then freezes or terminates the environment.

hello-world.ts

TypeScript

import { APIGatewayProxyHandler } from 'aws-lambda';

export const handler: APIGatewayProxyHandler = async (event) => {
  const { name = 'World' } = event.queryStringParameters || {};
  
  return {
    statusCode: 200,
    headers: {
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      message: `Hello, ${name}!`,
      timestamp: new Date().toISOString(),
    }),
  };
};

Event Sources

Lambda can be triggered by a wide variety of AWS services. Understanding these integrations is key to building effective serverless architectures.

Event Source	Invocation Type	Use Case
API Gateway	Synchronous	REST/HTTP APIs, webhooks
S3	Asynchronous	Process uploads, generate thumbnails
DynamoDB Streams	Synchronous	React to data changes
SQS	Synchronous	Process queue messages
SNS	Asynchronous	Fan-out notifications
EventBridge	Asynchronous	Scheduled tasks, event routing
Kinesis	Synchronous	Real-time stream processing

Common Lambda Event Sources

Best Practices

1Keep functions small and focused — single-responsibility principle applies
2Minimize cold starts by keeping deployment packages small and using provisioned concurrency for latency-sensitive workloads
3Use environment variables for configuration — never hardcode secrets
4Implement proper error handling and use Dead Letter Queues for failed invocations
5Monitor with CloudWatch metrics and X-Ray tracing for distributed debugging

“Serverless isn't about eliminating servers — it's about eliminating server management. The servers are still there; you just don't have to think about them anymore.”
S
Sarah Chen