Sorry for the late reply, Beehaw is blocking my phone’s ip cus of vpn.

Basically like blockchain yeah, where the state points to the previous state. I think it’s a combination of having to download all state events for the room (bandwidth), but also your server having to verify each and every event (cpu). It has to do all of this before you can really start using the room.

So if a user on your server joins a big room, it can put strain on the server until it got everything downloaded and verified.

Also, if for some reason (like someone spam joining the room) a lot of state events get generated, your server (and all other servers that connect to the room) have to download and verify each one of those state events.

For me, I only have my own user account on my server, and I only join private rooms. It’s a shame, cus the idea of Matrix is neat, but currently there’s no way to avoid getting DoS-ed if you join public rooms.