Apparently, Wikifunctions is a place to define e.g. mathematical formulas, so that they can be executed ad-hoc to provide insights about common questions.

Certainly makes sense to run those functions sandboxed in WebAssembly, since the function code is user-provided.
And then, yeah, I can imagine the process management making up a good amount of the complexity of their backend code...

Sharing, because I had to look up Abstract Wikipedia

Abstract Wikipedia is an in-development project of the Wikimedia Foundation. It aims to use Wikifunctions to create a language-independent version of Wikipedia using its structured data.

In this way, we can avoid relying on subprocesses and instead use threads (or, technically, asynchronous tasks) in Rust. Threads/tasks are much easier to manage

I believe, in their case cancelling a sync operation will not be a problem because they will not forever block on executing user-provided code, but cancelling a synchronous thread is not easy, afaik