Yeah but the way you're framing the problem is a bit crazy. If such a race condition is critical, then making A and B "otherwise independent" is a poorly desig

Yeah but the way you're framing the problem is a bit crazy. If such a race condition is critical, then making A and B "otherwise independent" is a poorly designed architecture (and, yes, novices will do this, which is why there is a big admonition in the Elixir docs: https://hexdocs.pm/elixir/master/GenServer.html#module-when-not-to-use-a-genserver https://hexdocs.pm/elixir/master/GenServer.html#module-when-...). Maybe they should all be branching logic or state machine in the same actor and you shouldn't be coordinating with message passing? If for some reason A and B TRULY need to be asynchronous and independent (let's say they are tracking real-world things), AND order matters, then no amount of language or VM architecture will get you out of building a transactional lock, consensus system, or CRDT to guarantee sane results. That is just how the universe works.