Wow they've been running 3.2 for this long? That's wild considering the talk Eileen gave at RailsConf this year made it sound like alot of the Rails 6 scalability stuff was based on GitHub's existing work.
They've been running 3.2 with local monkeypatches -- which is part of the reason that upgrading was problematic. (Though certainly not all; over that span, there were lots of breaking changes to supported and documented APIs.)
