I actually don’t have a particular scenario in mind. I have just been curious regarding this. But, since you ask about a possible scenario, consider Facebook. Do you think Phoenix/LiveView could scale to that?
CharlesIrvine
Wojciech
I don’t know much about facebook’s inner-workings so i don’t really know what could go wrong but facebook seems to do a lot of CRUD operations which is also the thing that Phoenix does very well so that won’t be an issue, the thing that elixir is not the best out of the box is building recommendations algorithms so you might have to use libraries such as Nx which communicates with other languages which are better at math, but besides that i don’t see anything that could get into the way.
1
al2o3cr
At Facebook-scale, nothing off-the-shelf works “as-is”. They build their own servers, build their own network routers, they even wrote their own PHP runtime.
5
CharlesIrvine
Kabawo
Since the OP’s original question was regarding social network messaging system I think ejabberd deserves an honorary mention.
1
joeb
Wojciech
Having big scalability requirements is a valid reason, but I chose Elixir & Phoenix mainly because I appreciate the design decisions made by its developers, which is also a valid reason even though it’s entirely subjective 
2