That's a great question. Answer: a lot of control. In order to run the cache experiment Vlad had to file an access control ticket which I had to approve. He wa

That's a great question. Answer: a lot of control. In order to run the cache experiment Vlad had to file an access control ticket which I had to approve. He was given access to cached images from two dogfooding/guinea pig machines and was able to run his experiment on those machines. They are not machines through which we run 'normal' production traffic.