It's slow. So we use hypothetical mostly for async experiences.

For live experiences like chat, we solved it with UX. As soon as you start typing the words of a question into the chat box, it does the FTS search and retrieves a set of documents that have word-matches, scored just using ES heuristics (eg: counting matching words etc)

These are presented as cards that expand when clicked. The user can see it's doing something.

While that's happening, also issue a full hyde flow in the background with a placeholder loading shimmer that loads in the full answer.

So there is some dead-time of about 10 seconds or so while it generates the hypothetical answers. After that, a short ~1 sec interval to load up the knowledge nodes, and then it starts streaming the answer.

This approach tested well with UXR participants and maintains acceptable accuracy.

A lot of the times, when looking for specific facts from a knowledge base, just the card UX gets an answer immediately. Eg: "What's the email for product support?"