We clone a running VM in 2 seconds

Summary

At CodeSandbox we run your development project and turn it into a link you can share with anyone. People visiting this link can not only see your running code, they can click “fork” and get an exact copy of that environment within 2 seconds so they can easily contribute back. Give it a try with this example, or import your GitHub repo here! So how can we spin up a cloned environment in 2 seconds? That's exactly what I'll be talking about here! The challenge: spinning up a development environment in two seconds We've been running sandboxes for a long time now, and the core premise has always been the same: instead of showing static code, it should be running. Not only that, you should be able to press fork and play with it whenever you want to. In the past, we've enabled this experience by running all your code in your browser. Whenever you would look at a sandbox, you would execute the code. This was fast, because we had full control over how the code was bundled. Forks were fast: However, there was a catch to this approach: we were limited to the code that we could run in the browser. If you wanted to run a big project that requires Docker, it wouldn't work. So for the past few years, we've been asking ourselves: how can we enable this experience for bigger projects? Firecracker to the rescue Virtual machines are often seen as slow, expensive, bloated and outdated. And I used to think the same, but a lot has changed over the past few years. VMs power most of the cloud (yes, even serverless functions!), so many great minds have been working on making VMs faster and lightweight. And well... they've really outdone themselves. Firecracker is one of the most exciting recent developments in this field. Amazon created Firecracker to power AWS Lambda and AWS Fargate, and nowadays it's used by companies like Fly.io and CodeSandbox. It's written in Rust, and the code is very readable. If you're interested in how it works, you should definitely check their repo! Firecracker s...