For developers using Java on a daily basis, JVM is a pretty important component - it runs our software. But it is usually treated like a magic box, which takes code in and produces business features. Have you ever thought about what you are missing with such an approach? During my talk, I'll cover some of the JVM internals which should not be avoided even during regular Java development. We'll discuss real differences between primitives and their wrappers, talk about the cost of using lambdas and streams, see what really gets erased in the type erasure process and what we can gain by removing stacktrace from our business exceptions.