AWS Lambda TypeScript Integration

Patterns for creating high-performance AWS Lambda functions in TypeScript with optimized cold starts.

Overview

Two approaches for TypeScript Lambda:

1. NestJS Framework - Dependency injection, modular architecture, larger bundle (100KB+)
2. Raw TypeScript - Minimal overhead, smaller bundle (<50KB), maximum control

Both support API Gateway and ALB integration.

When to Use

• Creating new Lambda functions in TypeScript
• Optimizing cold start performance
• Choosing between NestJS and minimal TypeScript
• Configuring API Gateway or ALB integration
• Setting up CI/CD for TypeScript Lambda

Instructions

1. Choose Your Approach

2. Project Structure

#### NestJS Structure

my-nestjs-lambda/
├── src/
│   ├── app.module.ts
│   ├── main.ts
│   ├── lambda.ts           # Lambda entry point
│   └── modules/
│       └── api/
├── package.json
├── tsconfig.json
└── serverless.yml

#### Raw TypeScript Structure

my-ts-lambda/
├── src/
│   ├── handlers/
│   │   └── api.handler.ts
│   ├── services/
│   └── utils/
├── dist/                   # Compiled output
├── package.json
├── tsconfig.json
└── template.yaml

3. Implementation Examples

See the References section for detailed implementation guides. Quick examples:

NestJS Handler:

// lambda.ts
import { NestFactory } from '@nestjs/core';
import { ExpressAdapter } from '@nestjs/platform-express';
import serverlessExpress from '@codegenie/serverless-express';
import { Context, Handler } from 'aws-lambda';
import express from 'express';
import { AppModule } from './src/app.module';

let cachedServer: Handler;

async function bootstrap(): Promise<Handler> {
  const expressApp = express();
  const adapter = new ExpressAdapter(expressApp);
  const nestApp = await NestFactory.create(AppModule, adapter);
  await nestApp.init();
  return serverlessExpress({ app: expressApp });
}

export const handler: Handler = async (event: any, context: Context) => {
  if (!cachedServer) {
    cachedServer = await bootstrap();
  }
  return cachedServer(event, context);
};

Raw TypeScript Handler:

// src/handlers/api.handler.ts
import { APIGatewayProxyEvent, APIGatewayProxyResult, Context } from 'aws-lambda';

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

Core Concepts

Cold Start Optimization

TypeScript cold start depends on bundle size and initialization code. Key strategies:

1. Lazy Loading - Defer heavy imports until needed
2. Tree Shaking - Remove unused code from bundle
3. Minification - Use esbuild or terser for smaller bundles
4. Instance Caching - Cache initialized services between invocations

See Raw TypeScript Lambda for detailed patterns.

Connection Management

Create clients at module level and reuse:

// GOOD: Initialize once, reuse across invocations
import { DynamoDBClient } from '@aws-sdk/client-dynamodb';

const dynamoClient = new DynamoDBClient({ region: process.env.AWS_REGION });

export const handler = async (event: APIGatewayProxyEvent) => {
  // Use dynamoClient - already initialized
};

Environment Configuration

// src/config/env.config.ts
export const env = {
  region: process.env.AWS_REGION || 'us-east-1',
  tableName: process.env.TABLE_NAME || '',
  debug: process.env.DEBUG === 'true',
};

// Validate required variables
if (!env.tableName) {
  throw new Error('TABLE_NAME environment variable is required');
}

Best Practices

Memory and Timeout Configuration

• Memory: Start with 512MB for NestJS, 256MB for raw TypeScript
• Timeout: Set based on cold start + expected processing time
• NestJS: 10-30 seconds for cold start buffer
• Raw TypeScript: 3-10 seconds typically sufficient

Dependencies

Keep package.json minimal:

{
  "dependencies": {
    "aws-lambda": "^3.1.0",
    "@aws-sdk/client-dynamodb": "^3.450.0"
  },
  "devDependencies": {
    "typescript": "^5.3.0",
    "esbuild": "^0.19.0"
  }
}

Error Handling

Return proper HTTP codes with structured errors:

export const handler = async (event: APIGatewayProxyEvent): Promise<APIGatewayProxyResult> => {
  try {
    const result = await processEvent(event);
    return {
      statusCode: 200,
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(result)
    };
  } catch (error) {
    console.error('Error processing request:', error);
    return {
      statusCode: 500,
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ error: 'Internal server error' })
    };
  }
};

Logging

Use structured logging for CloudWatch Insights:

const log = (level: string, message: string, meta?: object) => {
  console.log(JSON.stringify({
    level,
    message,
    timestamp: new Date().toISOString(),
    ...meta
  }));
};

log('info', 'Request processed', { requestId: context.awsRequestId });

Deployment Options

Quick Start

Serverless Framework:

service: my-typescript-api

provider:
  name: aws
  runtime: nodejs20.x

functions:
  api:
    handler: dist/handler.handler
    events:
      - http:
          path: /{proxy+}
          method: ANY

AWS SAM:

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31

Resources:
  ApiFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: dist/
      Handler: handler.handler
      Runtime: nodejs20.x
      Events:
        ApiEvent:
          Type: Api
          Properties:
            Path: /{proxy+}
            Method: ANY

Deployment Validation

Pre-deploy checks:

1. Run npm test - verify all tests pass
2. Run npm run build - confirm TypeScript compiles without errors
3. Verify bundle size < 50MB (unzipped)
4. Run serverless invoke local or sam local invoke - test locally

Post-deploy verification:

1. Run serverless invoke or aws lambda invoke - verify handler executes
2. Test API endpoint via curl or Postman
3. Check CloudWatch logs for errors
4. Verify cold start time meets SLA

For complete deployment configurations including CI/CD, see Serverless Deployment.

Constraints and Warnings

Lambda Limits

• Deployment package: 250MB unzipped maximum (50MB zipped)
• Memory: 128MB to 10GB
• Timeout: 15 minutes maximum
• Concurrent executions: 1000 default (adjustable)
• Environment variables: 4KB total size

TypeScript-Specific Considerations

• Bundle size: TypeScript compiles to JavaScript; use bundlers to minimize size
• Cold start: Node.js 20.x offers best performance
• Dependencies: Use Lambda Layers for shared dependencies
• Native modules: Must be compiled for Amazon Linux 2

Common Pitfalls

1. Importing heavy libraries at module level - Defer to lazy loading if not always needed
2. Not bundling dependencies - Include all production dependencies in the package
3. Missing type definitions - Install @types/aws-lambda for proper event typing
4. No timeout handling - Use context.getRemainingTimeInMillis() for long operations

Security Considerations

• Never hardcode credentials; use IAM roles and environment variables
• Input Validation for Event Data: All incoming event data (API Gateway request bodies, S3 event objects, SQS message bodies) is untrusted external content; always validate and sanitize before processing to prevent injection attacks
• Content Sanitization: When processing S3 objects or SQS message payloads, treat the content as untrusted third-party data; apply appropriate validation, schema checks, and sanitization before acting on it
• Validate all input data
• Use least privilege IAM policies
• Enable CloudTrail for audit logging
• Sanitize logs to avoid leaking sensitive data

References

For detailed guidance on specific topics:

• [NestJS Lambda](references/nestjs-lambda.md) - Complete NestJS setup, dependency injection, Express/Fastify adapters
• [Raw TypeScript Lambda](references/raw-typescript-lambda.md) - Minimal handler patterns, bundling, tree shaking
• [Serverless Config](references/serverless-config.md) - Serverless Framework and SAM configuration
• [Serverless Deployment](references/serverless-deployment.md) - CI/CD pipelines, environment management
• [Testing](references/testing.md) - Jest, integration testing, SAM Local

Examples

Example 1: Create a NestJS REST API

Input: Create a TypeScript Lambda REST API using NestJS for a todo application

Process:

1. Initialize NestJS project with nest new
2. Install Lambda dependencies: @codegenie/serverless-express, aws-lambda
3. Create lambda.ts entry point with Express adapter
4. Configure serverless.yml with API Gateway events
5. Deploy with Serverless Framework

Validation:

• Run serverless invoke local -f api - verify handler works
• Check bundle size < 250MB
• Test deployed endpoint returns 200 OK

Output: NestJS project with REST API, DynamoDB integration, deployment config

Example 2: Create a Raw TypeScript Lambda

Input: Create a minimal TypeScript Lambda function with optimal cold start

Process:

1. Set up TypeScript project with esbuild
2. Create handler with proper AWS types
3. Configure minimal dependencies
4. Set up SAM or Serverless deployment
5. Optimize bundle size with tree shaking

Validation:

• Run sam local invoke - test locally before deploying
• Verify bundle < 50KB with du -sh dist/
• Confirm cold start < 100ms via CloudWatch

Output: Minimal TypeScript Lambda, bundle < 50KB, cold start < 100ms

Example 3: Deploy with GitHub Actions

Input: Configure CI/CD for TypeScript Lambda with SAM

Process:

1. Create GitHub Actions workflow
2. Set up Node.js environment
3. Run tests with Jest
4. Bundle with esbuild
5. Deploy with SAM

Validation:

• Verify CI pipeline runs npm test successfully
• Confirm sam validate passes in pipeline
• Check CloudFormation stack created successfully

Output: GitHub Actions workflow, multi-stage pipeline, test automation

Version

Version: 1.0.0