Github is probably past the stage of premature optimization. Presume (for argument's sake) that we accept the premise that foreign keys do not scale. Then the

Github is probably past the stage of premature optimization. Presume (for argument's sake) that we accept the premise that foreign keys do not scale. Then the question is whether there exists some sort of realistic migration strategy once usage grows past that. If it does, then using FK makes total sense until we hit that point, doesn't it? And if true this should apply to 99% of users. But if there exists no such migration strategy, then maybe the guy has a point?