Have you ever been interested in the internal structure of the JVM? Have you ever had to tune the JVM at work?

Yes, I have studied the internal structure of the JVM quite deeply, including memory architecture, garbage collector operation, bytecode compilation into machine code via JIT, and optimizations. At work, I had to tune the JVM to improve application performance, especially in terms of adjusting garbage collector parameters (for example, choosing between G1, CMS, Parallel GC), heap size, Metaspace parameters, and thread settings.

An example of JVM tuning for an application with a large number of short-lived objects:

java -Xms4g -Xmx4g -XX:+UseG1GC -XX:MaxGCPauseMillis=200 -jar app.jar

This approach helps reduce pause times during garbage collection and increases the stability of the service.