A much better description is that doors is RPC-like but with priority and CPU quantum transfer to the server thread. This works great as long as the server thr

A much better description is that doors is RPC-like but with priority and CPU quantum transfer to the server thread. This works great as long as the server thread isn't itself doing slow I/O. The moment the server thread does slow I/O you want to get back to async I/O, and the whole point of doors is that it's synchronous because only by being synchronous do you get to transfer priority and CPU quantum from the client to the server. For async RPC-like schemes you cannot transfer priority and CPU quantum to the server because the client will continue executing with that same CPU quantum (that being implied by "async"). Also, this really only works locally. For remote services the server could get priority metadata from the client's authentication credentials, but that's it.