The Road to 2 Million Websocket Connections in Phoenix - Phoenix Blog is pretty old but it’s still relevant.

The million dollar question though is: What are those websockets doing? This blog post helps analyze the upper limit from the perspective of just raw open sockets, but the answer to your question could be “just 1” if the socket is moving gigs per second and you’re doing tons of processing on each byte.

Speaking in very general and vague terms though: If you’re doing “simple” things and on a “reasonably sized” webserver, you could probably do tens of thousands of subscriptions without even really thinking about it. You’re more likely to need to optimize your DB querying first.

You can go a long way before reaching a limit…

If You mean connections as in websocket, channels are multiplexed over socket.

It should not be something to worry about