AWS Lambda

AWS Lambda

Serverless functions with AWS Lambda, API Gateway, and event triggers.

Quick Start

import { Handler, APIGatewayProxyEvent, APIGatewayProxyResult } from 'aws-lambda';

export const handler: Handler = async (event: APIGatewayProxyEvent): Promise<APIGatewayProxyResult> => {
  return {
    statusCode: 200,
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      message: 'Hello from Lambda!',
      path: event.path,
      method: event.httpMethod,
    }),
  };
};

# template.yaml (SAM)
AWSTemplateFormatVersion: '2010-09-09'
Resources:
  HelloFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: src/
      Handler: index.handler
      Runtime: nodejs20.x
      Events:
        Api:
          Type: Api
          Properties:
            Path: /hello
            Method: GET

When to Use

• Event-driven serverless APIs
• Background processing (resize images, send emails)
• Not for long-running processes (>15 min)

Step-by-Step Instructions

1. Install AWS SAM CLI
2. Create SAM template with Lambda functions
3. Write handler code
4. Deploy: sam deploy --guided

Dependencies

# Install AWS SAM CLI
# https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/install-sam-cli.html
npm install aws-lambda @types/aws-lambda

Examples

Input: GET /hello → Output: { "message": "Hello from Lambda!" }

Resources

• AWS Lambda Docs
• Examples

Troubleshooting

• Cold start spikes — keep dependencies lean, enable provisioned concurrency for hot paths, and prefer lighter runtimes (Node/Go).
• Timeouts at 6s in VPC — the default Lambda timeout is too low. Raise the timeout and check NAT gateway routes to private subnets.
• Permission denied on SDK calls — the execution role lacks policy. Attach the least-privilege IAM policy and re-test with --no-sign-request.
• /tmp fills up — the 512MB scratch space is shared between invokes. Clean it in a finally block or use /tmp only for small artifacts.

Validation

1. Function deploys successfully
2. API Gateway endpoint responds
3. CloudWatch logs show execution