[redka]

Instead of cramming ecoded json into the data channels, like you'd with websockets, you can build binary buffers with all the data that has to be communicated between server and client. For example movement commands like up/down/left/right alongside some flags like isJumping can be packed into a singe uInt8

[vvanders]

Yup, delta compression and potential visibility sets are also a huge win as well.

The best thing is to design your gameplay to be "predictive", that's how we had ~300 player games like Subspace over 28.8/56k way back in the day.