Just-in-time is an illusion. Albert Einstein This week, Takashi Kokubun (@k0kubun) merged the first implementation of a JIT compiler in MRI ruby. k0kubun @k0kubun I've just committed the initial JIT compiler for Ruby. It's not still so fast yet (especially it's performing badly with Rails for now), but we have much time to improve it until Ruby 2.6 (or 3.0) release. github.com/ruby/ruby/commit/ed9