> He's also implying that Rails does not use web sockets to communicate with frontend which is not only wrong it should be evidently wrong to anyone who built a Rails app in the last 3 years.

I’m actually a rails dev but I’d reach for phoenix if my app required a large number of persistent sockets (e.g. high-volume MCP servers). I say this mostly because the hosting story is better for phoenix (gigalixir) than rails (heroku, or similar services that run behind a request router). Of course if you want your own infra this argument doesn’t apply. But a $100 gigalixir box can easily serve 100k persistent connections — even a few thousand persistent connections is a non-starter on Heroku.