WhatsApps original backend software was built in erlang
I thought that meant it’s not written in Erlang anymore and that was the reason of my first post to you. What I meant from my previous post that it’s doesn’t sound plausible that “pushing away” from Erlang is going to happen. Yes I’ll bet there has been talk about moving away from Erlang at Facebook at some point probably because messenger switched to I think C++. Switching from immutable language like Erlang to C++ that is much more error prone sounds crazy to me.
XMPP is just a protocol, you can use different transport channels, and Phoenix Channel is one of them. However in most cases there would be no point in that as Phoenix Channels are meant mostly for WebSockets and XMPP can use raw TCP connections. So if you want you can for example build Web UI for XMPP with Phoenix that would use Phoenix Channels for communicating with browser and use raw TCP in the backend.
My information could be wrong, but i recall reading that Facebook messenger was originally written in erlang and they did a full rewrite into c++ “because no one could understand the code” which is what cause the errors and bugginess for a long time.