serverless

Serverless

Serverless is a cloud-native development model for building and running applications without managing servers. The cloud provider handles the routine work of provisioning, maintaining, and scaling the server infrastructure.

When to Use

• Event-Driven Workloads: Processing file uploads (S3), stream events (Kafka/Kinesis), and asynchronous queue workers.
• Variable & Spiky Traffic: Applications with unpredictable request volumes scaling automatically from 0 to thousands of instances.
• Low-Maintenance Web APIs: Deploying micro-APIs or webhook handlers without managing servers, operating systems, or patching.
• Scheduled Background Tasks: Running cron jobs, batch data transformations, and reporting tasks via EventBridge / CloudWatch.

Quick Start

// AWS Lambda Handler (Node.js)
export const handler = async (event) => {
  console.log("Event received:", JSON.stringify(event));

  const name = event.queryStringParameters?.name || "World";

  return {
    statusCode: 200,
    body: JSON.stringify({ message: `Hello, ${name}!` }),
  };
};

# serverless.yml (Serverless Framework)
service: my-api
provider:
  name: aws
  runtime: nodejs20.x

functions:
  hello:
    handler: handler.hello
    events:
      - httpApi:
          path: /hello
          method: get

Core Concepts

Ephemeral Stateless Execution

Instances spin up on demand and shut down after idle periods; in-memory state is destroyed when containers terminate:

// AWS Lambda / Cloudflare Worker Handler
export const handler = async (
  event: APIGatewayProxyEvent,
): Promise<APIGatewayProxyResult> => {
  // Global variables persist across warm starts, but local handler state resets
  const result = await processItem(event.body);
  return {
    statusCode: 200,
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(result),
  };
};

Cold Start Lifecycle & Mitigation

Understanding initialization phases: