I would guess that aggressive caching and indexing are at least as important as having thousands of computers complete the request at once (and I'd be surprised

I would guess that aggressive caching and indexing are at least as important as having thousands of computers complete the request at once (and I'd be surprised if the number of computers on the request path is nearly that high--if nothing else, thousands of computers mean you're almost guaranteed to hit p999 latency every time).