The Senior Java Engineer's JVM Playbook

You know the feeling. You're three rounds into a senior or staff Java interview, and the interviewer asks something like *"what happens, step by step, when `java Foo` runs?"* or *"why is `ConcurrentHashMap.get()` lock-free?"* You can get to the two-level answer. But the third "why" — the one that separates Senior from Staff — is where you stall.

This playbook is built to close that gap.

It's a 66-page distilled reference covering every JVM topic that actually shows up in real senior/staff engineer interviews — organized so every concept can survive a *why → why → why* drilldown.