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CI NPM version Known Vulnerabilities js-standard-style

Inspired by the AWSLABS aws-serverless-express library tailor made for the Fastify web framework.

No use of internal sockets, makes use of Fastify's inject function.

Seems faster (as the name implies) than aws-serverless-express and aws-serverless-fastify 😉


$ npm install aws-lambda-fastify


aws-lambda-fastify can take options by passing them with : awsLambdaFastify(app, options)

property description default value
binaryMimeTypes Array of binary MimeTypes to handle []
serializeLambdaArguments Activate the serialization of lambda Event and Context in http header x-apigateway-event x-apigateway-context true
callbackWaitsForEmptyEventLoop See: Official Documentation undefined



const awsLambdaFastify = require('aws-lambda-fastify')
const app = require('./app')

const proxy = awsLambdaFastify(app)
// or
// const proxy = awsLambdaFastify(app, { binaryMimeTypes: ['application/octet-stream'], serializeLambdaArguments: false /* default is true */ })

exports.handler = proxy
// or
// exports.handler = (event, context, callback) => proxy(event, context, callback)
// or
// exports.handler = (event, context) => proxy(event, context)
// or
// exports.handler = async (event, context) => proxy(event, context)


const fastify = require('fastify')

const app = fastify()
app.get('/', (request, reply) => reply.send({ hello: 'world' }))

if (require.main === module) {
  // called directly i.e. "node app"
  app.listen(3000, (err) => {
    if (err) console.error(err)
    console.log('server listening on 3000')
} else {
  // required as a module => executed on aws lambda
  module.exports = app

When executed in your lambda function we don't need to listen to a specific port, so we just export the app in this case. The lambda.js file will use this export.

When you execute your Fastify application like always, i.e. node app.js (the detection for this could be require.main === module), you can normally listen to your port, so you can still run your Fastify function locally.


The original lambda event and context are passed via headers and can be used like this:

app.get('/', (request, reply) => {
  const event = JSON.parse(decodeURIComponent(request.headers['x-apigateway-event']))
  const context = JSON.parse(decodeURIComponent(request.headers['x-apigateway-context']))
  // ...

⚡️Some basic performance metrics

aws-lambda-fastify (serializeLambdaArguments : false) x 25,700 ops/sec ±2.28% (81 runs sampled)

aws-lambda-fastify x 23,981 ops/sec ±9.16% (76 runs sampled)

serverless-http x 16,969 ops/sec ±4.88% (73 runs sampled)

aws-serverless-fastify x 3,157 ops/sec ±1.91% (78 runs sampled)

aws-serverless-express x 2,569 ops/sec ±5.49% (75 runs sampled)

Fastest is aws-lambda-fastify (serializeLambdaArguments : false), aws-lambda-fastify


  • For apps that may not see traffic for several minutes at a time, you could see cold starts
  • Stateless only
  • API Gateway has a timeout of 29 seconds, and Lambda has a maximum execution time of 15 minutes. (Using Application Load Balancer has no timeout limit, so the lambda maximum execution time is relevant)
  • If you are using another web framework (Connect, Express, Koa, Restana, Sails, Hapi, Fastify, Restify) or want to use a more generic serverless proxy framework, have a look at: serverless-http

🎖Who is using it?

locize is using aws-lambda-fastify
localistars is using aws-lambda-fastify

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