Have you actually used old Mono? I remember sluggish performance, especially of its stop the world garbage collection.

Also, the standard library for ASP.NET either had gaps or somewhat incompatible implementations of features. I’d give time to attempt a port of a mid-size web forms app every couple years but ran into a number of issues each time.

It was an amazing achievement, but never quite got me there.

Mono had crap performance on .NET MVC and also some things just did not work. Mono would be horrible, horrible choice for website like SO.

Source: Was runnin .NET on Mono 7 years ago or so.

> Source: Was runnin .NET on Mono 7 years ago or so.

That's not a source. This is a source:

http://www.techempower.com/benchmarks/

Yes, it does show Mono's ASP performance is substantially worse than .NET, and probably more-so in 2008. I never said otherwise.

There are a lot of things to take into consideration when selecting a tech stack for a brand new, entirely unproven product. It's certainly on the list, however if performance ranks highly, then I'd be seriously questioning the diligence of whoever made said list. Expenditure (e.g. Windows Server licensing fees) would rank high on the list, however so would developer familiarity with a given stack as well as tooling familiarity.

As I said, I can see why StackOverflow made the decision they made, but I'm doubtful performance was, at that time, a major driving force.

no. Maybe ASP MVC4+ worked well with Mono, but WebForms and MVC below 4 was/is just horrible.