[lmm]

> if your app uses a database, you are incompetent not to employ an expert to help with the database, whether advising on the query plan of those non-performant queries, or what is the best setup for the current stage of the business and app, they are very useful

Given modern databases and modern hardware, I think the vast majority of applications never reach the point where query performance is an issue. For many small software companies hiring an expert in databases makes no more sense than hiring an expert in operating systems or networking - unless your needs are very specialized, these things work well enough out of the box.