Twitter is a massively distributed system with thousands of machines running thousands of JVMs. In any similar big system a small change in performance and CPU utilization is multiplied thousandfold and results in big savings. Electricity costs, cooling costs, and possibly reduction of server farm size. One way to improve Java performance and reduce CPU utilization is to simply generate better machine code. Simply is obviously not trivial but doable. Twitter is going down that road and experimenting with Graal to generate better code and reduce cost.