alt Hacker NewsHuh, that's interesting. Mixing indexes and FKs is a major conceptual error.
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.
I guess it depends on how much time you’ve spent in a relational db. For people who mostly interact with them via an orm, I can see where the confusion comes from.