I know it's possible to build a performant system without knowing how it works, it just isn't deterministically likely. There's also a difference between "buil

I know it's possible to build a performant system without knowing how it works, it just isn't deterministically likely. There's also a difference between "building a database", and "using a database". I'm not suggesting that people who write SQL should be able to write a DBMS (though that certainly helps) -- just that they should know, for example, how a B-tree index will most likely perform when joining two large tables. Or how storing a text column is different than a string. And so on. I've spent a lot of time cleaning up the messes of people who can write SQL -- sometimes, on large, heavily-used systems -- but had absolutely no idea why their multi-way joins were slow, or why doing LIKE queries over a large text column is a performance hit. These are stupid problems that anyone with basic CS knowledge can understand how to avoid. Aside: this is also the reason why fans of certain trendy technologies (...rhymes with bongo...) are routinely pilloried for making dumb technical decisions. Those who don't understand CS in theory are doomed to learn it in practice.