A minority of users run Ruby on the Windows Ruby Installer which targets mingw-x64 architecture. At least in my own case I use this as a convenience in development rather than in actual production.

Puma works on Windows with graceful degradation of features not supported by OS kernel like fork. It would be nice if Falcon could take a similar approach so that Windows users could at least use Falcon in development capacity (i.e. "it can serve single requests ok"). I've noticed the async gems are also failing to install on Windows.