Stack Overflow (which I avoid as much as I can fwiw) is not a strong argument for the .net stack given the people behind it have moved to a different stack for their next project (http://www.codinghorror.com/blog/2013/03/why-ruby.html). That's not an isolated incident.
I've several friends working in that stack. While many defend it as the correct decision at the time (and I don't disagree with that), all would rather be using something else now.
Most of the people behind Stack Overflow are still here...and we haven't changed our stack and are quite happy with the performance we get...and there's always more to squeeze out.
We can and sometimes do run Stack Overflow (currently 3.3 billions hit a month) from 2 web servers and 1 SQL server...I think that's pretty good for any stack.
Performance isn't the reason I see people wanting to move away from that stack; it's more about library availability, tool ecosystem (including things like monitoring, so this is an improvement - though I doubt it will stem the tide), and language productivity.
(Not that that your performance sounds like a compelling advantage for that stack. That's what, an average of 700 requests/second/web server? So the peak is probably around 1500? Pretty good indeed, but not outstandingly so - where I worked 3 years ago our system handled peaks of 600 requests/second/web server on a JVM-based stack. And I don't see .net topping the charts on http://www.techempower.com/benchmarks/).
First that chart's for linux systems...so it's not totally surprising to me that .Net isn't on it.
You have to keep in mind we're ridiculously over-provisioned, we're handling that load while maintaining 10-15% utilization on 3 year old web servers. Also, we're rendering quite a bit of dynamic data when rendering each page in < 40ms (the average for a question page on Stack Overflow yesterday was 36ms).
We render every request we get in a very speedy manner, usually with 90% headroom and utilizing only 1 DB server (also at only 10-15% utilization)...we're pretty happy with that.
> You have to keep in mind we're ridiculously over-provisioned, we're handling that load while maintaining 10-15% utilization on 3 year old web servers.
So you've premature-optimized for performance far past the point where you gained anything from it?
I'm not saying you shouldn't be happy with your performance, but if the best thing you can say about your platform is "it has adequate performance" then, well, it's not a very compelling platform.
I've several friends working in that stack. While many defend it as the correct decision at the time (and I don't disagree with that), all would rather be using something else now.