A sting of nostalgia and coincidence perhaps, was thinking about Java and HFT only a few days ago.

I worked as an offshore employee for E*Trade back in 2010 - 2012. Their desktop app for HFT was written in Java Swing and their web client too was running on the JVM but the 'services' layer the one that interacted with the database was written in C++.

Four years ago heard that they were re-writing the desktop app in JavaFX.