Too General question, well, ancient technology, why not the sockets?
Has a fallback with the polling.
But the key is that the websocket channel in fact.
On a well-loaded 8 core server holds 4-5K connections normally. Chokes when you restart of course)
Communication almost only in one direction, without receiving data from clients.
Not very suitable for communication in two directions, mainly to the distribution server.
In the two sides sharing the load immediately jumps to the skies and hangs.
In General, GO to portray something you for example.
Small ad implementation in a single process and a single thread was holding 2-3K users. Again, logic not only authorization and validation for alerts.
If gash sharding or multipotent, but 4-8 cores it is possible to hold 15K+.
Well NodeJS has not been canceled.
But in fact I gonoralisation NodeJS worked sucks than GO about 2 times less able to keep online 1500-1700, in the same single process and thread as the Go.
The implementation in both cases was on the knee, the functionality is the same.