You could write a FDW that reads/writes to a vector database using postgres id tagged vectors. You can write to it from postgres, reference it in queries, join

You could write a FDW that reads/writes to a vector database using postgres id tagged vectors. You can write to it from postgres, reference it in queries, join on it, etc. That cuts out a lot of the pain from having separate databases, the only remaining issues are additional maintenance overhead and hidden performance cliffs.