The entire basis of Erlang (well, it's VM, BEAM) are to be built from asynchronous primitives. From what I know, Phoenix works well with it. So yes, Phoenix do

The entire basis of Erlang (well, it's VM, BEAM) are to be built from asynchronous primitives. From what I know, Phoenix works well with it. So yes, Phoenix does "automatically parallelizes portions of an _individual_ request across multiple threads/cores using some special asynchronous dataflow-paradigm primitives or something." Edit: quoting you is not meant to be condescending... I'm not sure if it comes off that way or not. Edit 2: Not an expert and it may not be parallelized, but portions of the requess can be doled out to other threads, and when there's any down time from IO, other requests can use the thread...