I did a little bit of exploring a few years ago [0]. Iirc they just had one live stream for all their shows. All app events (quiz, chat messages) were through websocket.

The founders are ex-Vine founders, who then created a live streaming app called Hype. It looked like they were re-using Hype in HQ according to some URLs like hype.space.

https://github.com/Bekt/hqmania-ai/blob/master/lib/client.js

I found a job posting of theirs a while back while trying to figure out their tech stack. It required experience in docker, redis, node, can't remember what else if anything. Given the on demand nature of the game you can kind of imagine the kind of microservice architecture built from those components. For example each container handles X number of users, redis cache has a copy of game state/user state, each round questions/answers are handled and losers are kicked out so load is progressively reduced through the course of a game until only a winner remains. Most likely cloud was used to spin up containers right before trivia starts so you only pay for compute while a game is in progress then spin everything down.

If you have money (and they did) it’s actually not too difficult to solve. There are services out there to scale both video streaming[1] and websockets[2] for you.

[1] https://aws.amazon.com/cloudfront/streaming/ [2] https://pusher.com/