In my experience, Matrix is largely a protocol for defining groups of users across federation and sharing structured data in near real time between these users,

In my experience, Matrix is largely a protocol for defining groups of users across federation and sharing structured data in near real time between these users, with or without encryption. The main use case is definitely a chat protocol, but there's nothing preventing you from using this as a tuple-space-style database (I kind of am at the moment), or as a transmission layer for pretty much anything. I don't know about the current performance per server. I'm looking forward to seeing the Go and Rust implementations to compare performance :)