Mind sharing how it works and what stack you used?
Stack is quite simple:
Backend: PHP, MariaDB
The voice chat is done via https://meet.jit.si/
To handle potential big load, I force cloudflare to cache all sites under url /p/* thereby after the creation of the watch party, no request hits my server anymore :D
To enable this feature a browser plugin would be required again.
With Binge Together I opted for not supporting that in favor of an easier use. (Not everyone included needs to install the extension etc.)