"The basic architecture of Netflix Party is a client-server model. The clients connect to the server to synchronize their playback state. For the server, I wanted something low-latency that many clients could connect to at a time. Node.js fit the bill nicely."
Given the the model is traditional request/response (no push), wouldn't literally any web server tech fit this bill?
It looks like the backend is "dumb", and doesn't handle persistence (as it's not really needed), so using node allows the OP to simply store session state for clients on the stack as a global variable, so the server is completely independent and doesn't rely on any additional infrastructure. Most other backend techs (PHP, Ruby, most Python) simply handle the Request/Response cycle, with memory being cleared and allocated each time. Other web techs can do this, but node madebit easy " out of the box".
Given the the model is traditional request/response (no push), wouldn't literally any web server tech fit this bill?