To his credit, he sort of clarified that by implying it's "high traffic - for the sort of website that sits on 1 of 20 VM on a single physical server". If you do the naive multiply-everything-out-assuming-it-all-scales-linearly, 3% cpu on 1/20th of the physical server suggests an upper limit somewhere in the region of 165 million requests per day - that'd certainly count as a high-traffic site...

Well, high-traffic by certain standards. Higher-traffic than what seems to cause many server setups to fall over, anyway; front-page on HN or Slashdot doesn't send more than that much traffic, and yet a bunch of sites seem to be unable to handle it.