There's a few points that it doesn't get into: 1. it wasn't written in Erlang/Elixir or another BEAM language, 2. it's really more about gen_server than Erlang (a language), 3. if there are no replies then it's not an RPC but rather one-way data flow (which could have used Kafka/etc and not home-grown), 4. it can support multiple languages/runtimes.

ahoy!!! never expected to see any of my posts on hn D:

for the first point it was purposely not written on the beam as otherwise there would be no post!

an original draft of did talk more in depth about replies but it just got convoluted and too long!! maybe I'll try to restore something to this end

granted on the runtime and genserver point (though technically it's just a process that receives messages, nothing so formal as a genserver itself)

Not only gen_server, but OTP behaviors in general, IMO.