You can run your own simplex relay and it will be fast. But nostr already does it. So just use DMs.
I think that's being worked on.
This is from almost a year back but it's still coming I believe: https://youtu.be/7yjQFmhAftE
Discussion
The lag you're experiencing in groups doesn't depend on the relay.
It depends on the overall congestion of the network?
I don't know what you mean by "the network" in this case but it only depends on the number of group participants.
It seems to be a horrible design choice. What's the big O?
It's O(n) and yes they are aware of the limitations. It was better to get some version out quick even if it's imperfect I guess. The v2 will do it better.
There is a simplex-devs group you can join if you want to make constructive contributions. You can find it in the directory.
Thank you for a consise and informative response.
I can't even join groups because of timeouts. I'll end this comment without any scatalogical words to be nice 😁