Very many successful applications can indeed run on a single DB server (modulo redundancy in case of failures). Vertical scaling isn't trendy, but it is effecti

Very many successful applications can indeed run on a single DB server (modulo redundancy in case of failures). Vertical scaling isn't trendy, but it is effective, until it's not. I have yet to encounter a real situation where it suddenly became impossible to run a production DB on a single, high-spec server, without knowing far enough in advance to plan a careful migration to a horizontally scaled system if and when it was necessary.