I don’t understand the confidence that leads to such misuse. I’m NOT a db guy by any means, and yet when I need one I’m carefully looking up things like “what’s the space complexity of compound indices”, at a development stage. Defensive and paranoid. I guess there are a lot of cowboys out there.
Most people who use an index wrong dont understand space and time tradeoffs at all, how to measure if there is a problem, or how to identify what a thing should be in the first place.
Most people who at least think a bit get pretty far before the vendor specific gotchas start biting.
