I remember seeing a talk on the 2m websocket Elixir example and one of the keys to it was that the sockets were actually being used and processing messages intermittently during the test. Important thing to keep in mind vs simply opening.

The other thing I'd be interested to see Elixir demonstrate would be doing a hot deployment to avoid triggering all 2m connections to try reconnect at the same time.

The other important note with the Phoenix example was that they were starting 3 processes for each socket (to supervisor, handle failures/reconnects) if I remember correctly.