It’s half-baked actors. Well not baked at all (“no-bake actors”?) as isolated heaps and shared nothing is not easy to accomplish. OS processes can do it but they can be heavyweight. BEAM VM does a great job of it, though.
Share nothing is often too coarse grained serialization for all situations. Using a lock or other shared memory primitive (RCU, hazard pointers, etc) can lead to better performance due to smaller granularity of data protected and latency necessary to access the data. Optimizing for latency is very different from optimizing for throughput.
