WebSub: Open protocol for distributed pub–sub communication on the internet
"Hub deliver content to each subscriber with a POST"It's quite common on some social networks to have several thousands/millions subscribers for some pages/communities/accounts.Is it really wise to build a publish-subscribe delivery system on top of HTTP? This seems to be a huge overhead.In the meantime XMPP is already offering similar features (XEP-0060: Publish-Subscribe https://xmpp.org/extensions/xep-0060.html) for more than 10 years.
It's implemented in several servers and can handle huge loads without problems (everything is handled in real-time through encrypted TCP sockets accross the network).We are building social networks on top of XMPP for several years now, you can check Movim (https://movim.eu) and Salut à Toi (https://salut-a-toi.org/) :)