The team behind matrix.org had one prior to Matrix very similar to this too (albeit longpolling) called Glow. It was basically simple & stupid pubsub on top of

The team behind matrix.org had one prior to Matrix very similar to this too (albeit longpolling) called Glow. It was basically simple & stupid pubsub on top of HTTP: you could GET an arbitrary url, and whenever anyone PUT stuff within that url tree your GET would return. It worked well enough to build a pretty massive instant messaging platform on top of it, but the lack of schema and lack of intelligent query language got a bit frustrating. Some of the ideas made it into Matrix though. Braid looks cool; we've hoped someone would layer OT or CRDT semantics on top of Matrix but it hasn't really happened yet (unless you count Matrix itself as a set of add-only monotonic DAG CRDTs, which I guess it is). Eitherway, perhaps going in at a lower level like Braid has legs; time will tell :)