Optimizing Production Performance with MRI JIT by Takashi Kokubun Since we introduced a JIT compiler to Ruby in 2.6, it had been known to slow down production applications like Rails. This year, we finally figured out why it was the case and found a way to fix it. Now we can even see the JIT compiler of Ruby 3.0 optimizes one of the most popular Rails applications. In this talk, you'll learn some tricks to make sure it happens on your production application. Get the easy speedup of your application for free!