It usually came from serializing and deserializing objects which here it’s a shared json buffer? But even then there’s a serialization bottleneck right? You’d have to be mindful about how the context and closures work across boundaries. Then there’s also spinning up the workers, but I suppose you could do this ahead of time. Maybe my complaint is self-inflicted and is ultimately avoidable - but the complexity begins to mount.

There’s also the queuing and blocking nature of web-workers, I wish they could asynchronously process messages the same way js IO works, but that’s not the case. Rather you are batching full units of work. The mental model is different.

Anecdotally in Firefox I must have run into some memory leak issues and had to hard restart.

Ultimately I ended up going with service workers, which yes sounds strange but I found to be much easier to work with. Cancellable requests, async, long living in the background … but maybe it just works best for me ;)