That's reason why I think the push to follow event-driven (reactive) approaches in ecosystems like Java is doomed to fail (okay, that may be a bit harsh) because there is lot of existing blocking code. It will take a long time until all of the old libraries catch up. It kind of splits the whole ecosystem into half. Specifically in Java I think it's fine we are relying on blocking APIs (and threads). For most stuff it scales properly, doesn't feel unnatural and is easier to understand. I say this as a big fan of JavaScript, I just don't see the approach being introduced after the fact as a good idea.