It really varies, there's no consistent mapping. I'm at a fairly large company, literally all of our interview questions are pulled from the code base. We have

It really varies, there's no consistent mapping. I'm at a fairly large company, literally all of our interview questions are pulled from the code base. We have many hard problems that we can easily map to the standard "rankings" (easy, medium, hard) in e.g. leetcode if we want. I'd say most companies pull from sites like leetcode though.