> but in once case you need to have deep-ish understanding of the optimizer and SQL I will never understand why devs think they need to understand their chose

> but in once case you need to have deep-ish understanding of the optimizer and SQL I will never understand why devs think they need to understand their chosen application well, but not SQL. Your application relies on SQL, so why shouldn't you deeply understand it? Relational algebra isn't that complex compared to other things we take for granted as necessary.