(from Hasura)
Scaling subscriptions is hard, but we work with our users/customers at scale to make sure settings are tweaked correctly.
We have users running 100k - 1M concurrent users in production for live-event type platforms. It's not completely trivial to benchmark and setup because query patterns, streaming vs live queries etc have an impact, but it works very reliably. No missing events, no problems disconnecting/reconnecting, no need for sticky sessions and so on.
An initial POC benchmark [1] should be a quick affair so if you're trying it out and run into any problems, please hit me up! Email on my bio.