For people who run thousands of QPS on billions of vectors, Milvus is a solid choice. For someone playing with a twitter demo with a few thousand vectors, any vector db can do the job well. In fact there is a fun project Milvus Lite designed for that case :)

I've seen many builders migrate from pgvector to Milvus as their apps scale. But perhaps they wish they had considered scalability earlier.

(I'm from Milvus so i could be biased.)

Then, what if you want hybrid search, or different IVF variants, or disk-based search, or horizontal scaling, or something that leverages SIMD, or sparse vectors? Milvus is great.

Like others have already said, pgvector is used a lot as well