I'm not sure how i feel about this. On one hand, squeezing that sort of performance out of Heroku is a notable achievement. Props. On the other hand... why Heroku at that scale? 10x F-Large servers is going to cost 5-10x the cost of a comparable E3 configuration and E3 root access gives you a great deal more "knobs" for customizing your performance outside of your code.

I get that many teams don't want the overhead of managing their own instances, but when you find yourself optimizing for a platform that is engineered around convenience instead of performance i think it may be time to make the switch.