A little off-topic, but AWS has a service (actually 2) specifically for managing websocket communications. API Gateway supports an unlimited (you need to ask f

A little off-topic, but AWS has a service (actually 2) specifically for managing websocket communications. API Gateway supports an unlimited (you need to ask for an increase from the 500 new connections per second rate) number of connections and is only around $0.25 per million minutes + $1 per million messages. So just having 250,000 connections open would cost only around $270 per month (and scales up and down as you please).