It would have helped the author's case to try (at least approximately) replicating Digg's performance problem on a local MySQL install before switching technolo

It would have helped the author's case to try (at least approximately) replicating Digg's performance problem on a local MySQL install before switching technologies - that would have given some indication that he'd made the right assumptions about the problem and wasn't testing something unrelated. No matter how good the author is (and I've got no reason to suspect that he's anything other than a top-rate engineer), it's awfully easy to be led down a blind alley on this sort of problem.