So Denny Denker, the Ticketmaster chief architect, wrote a VAX Assembly language realtime ticketing operating system. He wrote it in the 70s, before things like TCP/IP were standardized, and they managed to virtualize it on Linux using a hacked up vax emulator[1]. They've tried many many times (when I was there around 2007ish) to rewrite it using normal things like C++ and mysql, yet couldn't manage to get it faster than a specialized realtime operating system. It was kind of hilarious when we moved it to NFS, as the operating system timed writes to the speed of the PDP-11 drive spin rate. When we moved it to NFS, the IO was 1000x faster, and the entire thing crashed. No end of jokes resulted from these sorts of "quirks" in our systems.
Last I've heard, they've been slowly moving functionality out of the VAX operating system into a more traditional stack.
Source: I used to work on the team responsible for the Linux servers that ran these virtualized vaxen, check the resume linked in my profile.