It's a single server with 32core/64 thread AMD EPYC and 128GB RAM.
At the moment we run multiple containers for lemmy so restarting doesn't mean outage.
Same happened with mastodon.world in November. Family goes first, then work, and then all of my hobbies, of which this is one. (But the one taking up most time at the moment...)
I think I use all chat software there is. I'm in hundreds of Matrix rooms. But I think one of the team at least didn't like or use Matrix. Don't remember. And I have Discord anyway for the Mastodon channels..
Yes phiresky is working with us improving performance, has helped a lot so far! (We're now running a custom build with some of his improvements)