Server-Sent Events: an alternative to WebSockets
I made the backend for this MMO on SSE over HTTP/1.1:https://store.steampowered.com/app/486310/Meadow/We have had a total of 350.000 players over 6 years and the backend out-scales all other multiplayer servers that exist and it's open source:https://github.com/tinspin/fuseYou don't need HTTP/2 to make SSE work well. Actually the HTTP/2 TCP head-of-line issue and all the workarounds for that probably make it harder to scale without technical debt.