Almost all of Twitter’s services run on the Java Virtual Machine platform. We have a team of engineers who work on performance improvements to our own custom version of the OpenJDK JVM. We are also active participants in the development of the Java platform and are members of the Java Community Process (JCP) Executive Committee (EC), helping provide oversight and stewardship of the Java platform and its evolution.
Source:: Twitter’s Vote on JSR 376 (Java Platform Module System)