What advantage are vector databases providing above using an index in conjunction with a mature database? I’m not sold on this as a separate technology. Vector search is useful, but I don’t understand why I would go out of my way when I could implement FAISS or HNSWlib as an adjunct to postgres or a document store.
But what is most times needed instead of a vector database is a efficient fast responsive vectore approximate KNN search system with fast attribute filtering which overlaps with a fast an efficient text search system (e.g. bm25 based)
And if you then go to billion vector scale things become tricky performance wise.
And then you reach the same point at which companies do things like using warehouse approach where you have a read only extremely read optimized mostly in memory variant of their db they access for searches only and changes from their main db a streamed to the read only search instance, potentially while losing snapshot views, transactions and similar.
You could say that approx. KNN vector search is the new must have feature for unstructured fuzzy text search, and while you can have unstructured fuzzy text search in pg it's also often not the go-to solution if your databse is just for getting that search.