And despite that I’m reprimanded by the forum for posting multiple replies, I feel compelled to address this point again…
Even in the simple “single socket, single stream, multiple subscribers” case, the notifications are sent in parallel - i.e. any given notification is sent in parallel to all subscribers. If this isn’t obvious from my earlier replies, perhaps you need to re-read them, or ask for clarification. This works just fine for “bursts” of notifications, where the fast subscribers can receive notifications “as fast as possible”.
Only when you continuously send notifications at a rate that the slow subscribers can’t handle will the SSH/TCP flow control kick in for them, and limit the rate at which notifications can be sent. But even then, each notification is sent is sent in parallel to all subscribers. Solving this “rate limiting” problem is hard - I can’t really think of a solution other than a) “somehow” requiring that subscribers can actually handle the steady-state rate of notifications, or b) providing “lite” versions of the streams for the slow subscribers, where fewer notifications are sent.