How to Get Foreign Keys Horribly Wrong

My assumption is that people have used orms that automatically add the index for you when you create a relationship so they just conflate them all. Often they’ll say that a foreign key is needed to improve the performance and when you dig into it, their mental model is all wrong. The sense they have is that the other table gets some sort of relationship array structure to make lookups fast.

It’s an interesting phenomenon of the abstraction.

Don’t get me wrong, I love sqlalchemy and alembic but probably because I understand what’s happening underneath so I know the right way to hold it so things are efficient and migrations are safe.

FWIW, I've also asked everyone I've interviewed in the past decade about indexes and FKs. Most folks I've talked to seem to understand FKs. They're often fuzzier on the details of indexes, but I don't recall anyone conflating the two.