HotSpot's optimizing Just-In-Time compiler C2 is reaching its end-of-life andit's time to look for alternatives. One very promising replacement candidateis Graal. Graal is a Java JIT compiler written in Java. It is being developedby Oracle Labs for a couple years now and has reached a state where it'sviable to be that replacement. Twitter's huge distributed system tickles everycorner of the JVM and is the perfect testing ground for a new JIT compilertechnology like Graal. This presentation will talk about Twitter's experienceswith Graal, good and bad, the bugs we found and also the wins.