not op either but I built my entire startup using elixir. We have a realtime sync component across a range of devices that sync data between them.

It (phoenix channels) worked out of the box. in the last 6 years of development and growth, not once have we ever had to even discuss scaling issues related to it.

It just works and when you're in a startup, the more you can focus on growing your product instead of scaling issues, the more you're winning.