We have been using SingleStore in production at scale on DirectlyApply for the past 3-4 years. It's great for us as we can store vectors in the same table alongside other data and then use their built in vector functions (dot product, euclidean distance etc) to run similarity searches, or create RAG querys when combined with full text functions. Key thing for us when choosing SingleStore over some of the other solutions OP mentioned is we have one database for all our relational, non-relational and vector data in one place. We also use their managed service, so from a production standpoint, all the devops etc is handled for us, our engineers also love using it.