aws-serverless-express

What is aws-serverless-express?

The aws-serverless-express package allows you to easily run Node.js web applications, such as those built with Express, on AWS Lambda and Amazon API Gateway. It simplifies the process of creating serverless applications by handling the integration between Lambda and API Gateway, allowing you to focus on your application logic.

What are aws-serverless-express's main functionalities?

Create a Serverless Express Application

This feature allows you to create a serverless Express application that can be deployed on AWS Lambda. The code sample demonstrates how to set up a simple Express app with a single route and export a Lambda handler that uses aws-serverless-express to handle incoming requests.

const awsServerlessExpress = require('aws-serverless-express');
const app = require('express')();
const server = awsServerlessExpress.createServer(app);

app.get('/hello', (req, res) => {
  res.send('Hello, world!');
});

exports.handler = (event, context) => awsServerlessExpress.proxy(server, event, context);

Custom Lambda Proxy Integration

This feature allows you to customize the Lambda proxy integration, such as specifying custom binary MIME types. The code sample shows how to create a server with custom binary MIME types and handle requests with a custom route.

const awsServerlessExpress = require('aws-serverless-express');
const app = require('express')();
const server = awsServerlessExpress.createServer(app, null, ['*/*']);

app.get('/custom', (req, res) => {
  res.json({ message: 'Custom integration' });
});

exports.handler = (event, context) => awsServerlessExpress.proxy(server, event, context);

Middleware Support

This feature demonstrates how to use middleware in your serverless Express application. The code sample shows how to log incoming requests using middleware and handle a route that responds with a message.

const awsServerlessExpress = require('aws-serverless-express');
const app = require('express')();
const server = awsServerlessExpress.createServer(app);

app.use((req, res, next) => {
  console.log('Request received');
  next();
});

app.get('/middleware', (req, res) => {
  res.send('Middleware example');
});

exports.handler = (event, context) => awsServerlessExpress.proxy(server, event, context);

Other packages similar to aws-serverless-express

serverless-http

The serverless-http package is a similar tool that allows you to run web applications on AWS Lambda. It supports various frameworks like Express, Koa, and Hapi. Compared to aws-serverless-express, serverless-http offers broader framework support and a simpler API for converting your web application into a Lambda-compatible handler.

lambda-api

The lambda-api package is a lightweight web framework designed specifically for AWS Lambda. It provides a similar experience to Express but is optimized for serverless environments. Compared to aws-serverless-express, lambda-api is more lightweight and tailored for Lambda, offering better performance and lower cold start times.

express

While not a direct competitor, the express package is the core framework that aws-serverless-express is designed to work with. Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. aws-serverless-express leverages Express to create serverless applications, whereas Express itself is not inherently serverless.

README

AWS Serverless Express

Run serverless applications and REST APIs using your existing Node.js application framework, on top of AWS Lambda and Amazon API Gateway. The sample provided allows you to easily build serverless web applications/services and RESTful APIs using the Express framework.

Getting Started

npm install aws-serverless-express

// lambda.js
'use strict'
const awsServerlessExpress = require('aws-serverless-express')
const app = require('./app')
const server = awsServerlessExpress.createServer(app)

exports.handler = (event, context) => awsServerlessExpress.proxy(server, event, context)

Package and create your Lambda function, then configure a simple proxy API using Amazon API Gateway and integrate it with your Lambda function.

Quick Start/Example

Want to get up and running quickly? Check out our example which includes:

• Lambda function
• Express server Swagger file
• Serverless Application Model (SAM)/CloudFormation template
• Helper scripts to configure, deploy, and manage your application

Getting the API Gateway event object

This package includes middleware to easily get the event object Lambda receives from API Gateway

const awsServerlessExpressMiddleware = require('aws-serverless-express/middleware')
app.use(awsServerlessExpressMiddleware.eventContext())
app.get('/', (req, res) => {
  res.json(req.apiGateway.event)
})

Is AWS serverless right for my app?

Pros

• Pay for what you use
• No infrastructure to manage
• Auto-scaling with no configuration needed
• Usage Plans
• Caching
• Authorization
• Staging
• SDK Generation
• API Monitoring
• Request Validation
• Documentation

Cons

• For apps that may not see traffic for several minutes at a time, you could see cold starts
• Cannot use native libraries (aka Addons) unless you package your app on an EC2 machine running Amazon Linux
• Stateless only
• API Gateway has a timeout of 30 seconds, and Lambda has a maximum execution time of 5 minutes.