V8 isolates are a way to run JavaScript code in separate contexts. Each isolate has its own heap and is completely isolated from other isolates, so that they cannot access each other’s memory. This is useful for running untrusted code in a sandboxed environment, or for running code in parallel to take advantage of multi-core processors.
Isolates are used by Node.js to run JavaScript code in separate threads, and by Chrome to run JavaScript code in separate tabs. V8 isolates is also the architecture behind Cloudflare Workers, and it is what allows developers to run JavaScript code at the edge of the network.
Cloudflare Workers use isolates to run Javascript code at the edge of the network instead of relying on a centralized server, containers or virtual machines. By doing so, Workers are able to use the V8 engine to run JavaScript code in a secure and isolated environment, and to take advantage of the performance benefits of running code and performing tasks close to the end user.
Differently from other serverless functions providers, Cloudflare Workers doesn’t create virtual machines or containers for each function, but instead create V8 isolates in an existing environment, making it faster and more efficient to run code as it prevents issues as cold starts that can delay the execution of the function.