Neat trick. He used [blitz.io](http://blitz.io/) to test this. Out of curiosity I ran a similar test using blitz.io on this site, without making a single change, just to see what happened. Here’s the result:
Not too shabby, but I wanted to push it a little further — so I did. ((250 concurrent users in 30 seconds.)) Here’s what I got:
That is roughly 19 million hits in a day. I monitored the CPU load during that test and it peaked at 80% and settled around 68%. No too shabby. ((I don’t know how “real” this testing system is, but it is pretty neat.))