Once upon a time I worked in the field of Java Optimizations. The target system was a distributed data processing platform that ran across hundreds of thousands of machines. At such scales, a 0.5% improvement would easily make up my salary going forward, and 2% was a good result for the half. That doesn’t mean it was easy. Never have I ever seen such a highly optimized Java codebase. Not before, not since. Every low hanging fruit had long since been picked clean. For example, there was minimal u...