Speakers: Brett Cannon, Dino Viehland At PyCon US 2015 an experiment was started: could a JIT be added to CPython which would speed up performance **and** be fully backwards-compatible? Could unaltered extension modules live happily with a JIT? That experiment is Pyjion and this talk will explain what we changed to CPython to add a pre-existing JIT to it and whether we met our goal of being a benefit instead of a hindrance. Slides can be found at: https://speakerdeck.com/pycon2016 and https://github.com/PyCon/2016-slides