Lambda Express

What?

An express-like framework for use with AWS Lambda functions that supports both API Gateway and Application Load Balancer integrations with Lambda.

The entire library is written in TypeScript so you get great autocomplete if you're using VS Code or similar. It's also very well tested, so you can rest assured that it will do what you need, and regressions between versions will be rare.

Why?

You shouldn't have to think about how API Gateway or Application Load Balancer send you request events, or how you need to respond to them with your responses. There are a lot of little intricacies, especially if you are using API Gateway for some of your APIs and Application Load Balancer for others (see this writeup for the differences).

If you're writing APIs, you've probably already written Express apps, so keeping things familiar will accelerate your development, allowing you to focus on your business logic.

Usage

Here's a simple example to get you up and running quickly:

npm i @silvermine/lambda-express

npm i -D aws-lambda

import { Application, Response, Request } from '@silvermine/lambda-express';
import { RequestEvent } from '@silvermine/lambda-express/dist/types/request-response-types';
import { NextCallback } from '@silvermine/lambda-express/dist/types/interfaces';
import { Context, Callback } from 'aws-lambda';

const app = new Application();

app.all('/*', (_request: Request, response: Response, next: NextCallback) => {
   response.set('Access-Control-Allow-Origin', '*');
   next();
});

app.options('/*', (_request: Request, response: Response) => {
   response.set('Access-Control-Allow-Methods', 'OPTIONS,GET')
      .set('Access-Control-Allow-Credentials', 'false');
   response.send('');
});

app.get('/my-endpoint', async (request: Request, response: Response) => {
   response.send('Hello world!');
});

// Use the helper function to create an async handler (Recommended for Node.js 18+)
export const handler = createAsyncHandler(app);

// Or use runAsync directly:
//
// export const handler = async (event: RequestEvent, context: Context): Promise<ResponseResult> => {
//    return app.runAsync(event, context);
// };

// Or for Node.js <24.x, use the callback style:
//
// export const handler = (event: RequestEvent, context: Context, callback: Callback): void => {
//    app.run(event, context, callback);
// };

At this point you should be able to compile, bundle, and deploy this Lambda. Assuming you have configured APIGW or ALB to forward traffic to your Lambda, you will now have a very basic working API!

Note: Both handler styles (async/await and callback) are supported for Node.js <24.x. However, the async/await style is recommended for Node.js 18+ and is required for Node.js 24+.

License

This software is released under the MIT license. See the license file for more details.