Run serverless Deno in AWS Lambda

Brian Leroux’s avatar

by Brian Leroux


This post was last updated May, 2020 as Deno hit 1.0

JavaScript is the most popular programming language in the world, and Deno is a very promising new JavaScript runtime with a lot of compelling new capabilities.

Begin is a serverless / FASTstack app platform based on AWS, and it enables frictionless delivery to AWS Lambda. This is like chocolate and peanut butter (or perhaps chocolate and cherries if you have a peanut allergy) — two great tastes that taste great together.

Try it out right now

Want to skip to the part where you’re building a serverless Deno app? Just hit this button to deploy a new Hello World! Deno app to Begin in 15 seconds:


Roll your own serverless Deno app (with Begin)

Begin checks each HTTP function for a .arc-config file, which is used to configure its corresponding Lambda from the default (Node 12.x) to Deno (latest stable).

# src/http/get-index/.arc-config

Your Lambda will now look for a TypeScript (or plain JS) handler at src/http/get-index/index.ts, here’s an example that returns Deno specific APIs:

export async function handler(req) {
return (body: JSON.stringify(Deno.versions))

Thanks to Deno, standard ES modules are natively supported and work as they would work in a web browser. You can import local modules with relative paths:

import render from './render.tsx'
export async function handler() {
    return {
        headers:{'content-type': 'text/html, charset=utf8'},
        body: render(Deno.versions)

And remotely hosted modules with fully qualified URL paths:

import React from 'https://dev.jspm/to/react'
import ReactDOMServer from 'https://dev.jspm/to/react-dom/server'
import { DenoVersion } from './deno.tsx'

export default function render(version: object) {
    let body = ReactDOMServer.renderToString(<DenoVersion version = {version} />)
    return `<doctype html>
    <main id=root>${body}</main>
    <script type=module src=/_static/browser.js></script>

Any fully qualified URL to a valid ES module will work!

As you probably noticed, the TypeScript and JSX dialects are also natively supported. Deno is really fun for frontend! Local development is also fully supported with the @architect/sandbox:

Deno running in sandbox

Considerations and trackable issues

  • Deno is progressing quickly, but know that it’s an early runtime, and remember that (for now) we’re doing this for fun and experimentation.
  • We (Begin) run a distribution of very recent versions of Deno built specifically for Lambda; it should be identical to your local Deno, just as Lambda Node.js is identical to your local Node.js.
  • An official Deno runtime distribution with AWS SAR is also apparently underway; this may eventually become the official AWS Lambda distribution.
  • Persistence with Begin Data (@begin/data) for Deno is planned: follow progress here.
  • OpenJS Architect-style code sharing between Deno Lambdas is planned: follow progress here.

Next steps

  • Deploy a simple Hello World! Deno app to Begin in 15 seconds. What are you waiting for, anyway?