I don't federate. If I had more control over how much data other servers could dump on my server, other than restricting rooms with X number of users, I would. Synapse and Element together are heavier than any other chat servers/clients I've ran, with only one exception.

It is not a big problem, because my number of active users is fairly small (under 50), but I could see myself having to use a different server software, or possibly a different protocol all together, if it were to open up and grow.