[kasey_junk]

Having written a few low latency systems a few of which are on the JVM, I will say that in all of those cases, allocating/freeing memory is always a slow down regardless of GC or not (cache coherence is almost always the deal breaker here). So in those systems, you simply do not allocate/deallocate along the critical path.

Is this difficult in Java? Yes. It's also difficult in C++. Just because it is difficult doesn't mean it is impossible.

So if I am resorting to managing my own memory anyway, why would I use the JVM? Because typically the code that is on the critical path is a small percentage of the entire code base, and the other advantages of the JVM (tooling, language features, libraries etc.) out way the downsides.

That's not always the case, and I don't have any specific knowledge of Kafka, but just because something needs to be low/consistent latency doesn't mean it can't (or shouldn't) be written on the JVM.