As in many other languages, in Java heap memory is managed. That is, the program explicitly reserves memory, but does not indicate when to free it and delegates it to the garbage collector.

This way to deal with memory has several advantages, but it also has some drawbacks that become more problematic when the program has to work with a large amount of data or process it very quickly. For example systems like Apache Kafka or databases like Apache Pinot largely avoid using managed memory and instead manually allocate and free memory in what is known as offheap memory.

This is a technical and practical talk about how to use this memory in the JVM, when it's worth using it, and how it affects our code and deployments including examples in real applications and libraries.