Curious if the author tried the new Redis module that brings HNSW vector search to redis.

From what I've seen is fast, has excellent API, and is implemented by a brilliant engineer in the space (Antirez).

But not using these things beyond local tests, I can never really hold opinions over those using these systems in production.

It's not a module, it is part of every new Redis version now. Well, actually: it is written in the form of a module and with the modules API in order to improve modularity of the Redis internals, but it is a "merged module", a new implementation/concept I implemented in Redis exactly to support the Vector Sets use case. Thank you for mentioning this.

It's fast...because everything needs to be in memory. Expect astronomical cloud costs even for mid-sized data requirements.