It's dreadfully common to not understand database performance. Junior engineers I can understand, they're given a task and hack it together and don't understand

It's dreadfully common to not understand database performance. Junior engineers I can understand, they're given a task and hack it together and don't understand why it's slow, but at least it works. But I've seen some pretty shitty work from "senior" engineers too. They know how to put a product together but they shy away from the database besides creating the table itself.