That's funny, because I've been taking servers full of large blocking thread pools, rewriting them to be non-blocking, idiomatic Scala, Cats Effect 3 and get +5

That's funny, because I've been taking servers full of large blocking thread pools, rewriting them to be non-blocking, idiomatic Scala, Cats Effect 3 and get +50% throughout. Blocked threads are seriously bad for performance. Yes, Java 21 project Loom will help with that (finally), if people get with the program. There aren't any race conditions, because our classes and data model are fully immutable. The problem with our legacy servers was that the original devs didn't know what monads were, and decided not to use them. Error handling is now great, by using... you guessed it, monads.