We use Crossbar and WAMP to build Simpl (https://simpl.world/ https://simpl.world/) on overall it's been a great experience. Definitely suffers from some of th

We use Crossbar and WAMP to build Simpl (https://simpl.world/ https://simpl.world/) on overall it's been a great experience. Definitely suffers from some of the challenges mentioned above (commercial clustering, large-ish frontend libraries, etc) but it's been pretty straight forward to work with and scales up well enough for our needs (a few hundred to a few thousand simultaneous concurrent players).