[eranation]

How much does the fact you have non blocking green threads matters when you have a cluster of 100 machines? Yes, internally in each machine there are less kernel threads and less overhead, but If an actor on one machine sends a message to an actor in another, does it matter if it's a jvm thread or a fiber?

[circlespainter]

If you want regular code and not async, then yes, it matters: if you have a lot of OS thread-based actors performing blocking network "send"s as part of their regular control flow, each of them blocks an OS thread and you'll run out of resources soon. If those actors are backed by lightweight threads instead, which are very frugal, basically you are only limited by the network stack.

[eranation]

My thought is that always the network is the bigger bottleneck. But I guess it depends on the data / OS etc.