I use workers in deno to evaluate user facing code which may take a lot of time to finish and need sandboxing. Another place it's used in where I want to keep context and reuse it for subsequent code execution for each user.

In deno, you can restrict what the code inside worker can do by passing a map of allowed permissions. I have built a simple privilege system on top of this to allow users different access level.

This is cheaper and faster than spinning up container.