Nostr does suck. The NDK that much of the nostr protocol is running on is BAD. Very, very non-performant. nostr:nprofile1qqs99d9qw67th0wr5xh05de4s9k0wjvnkxudkgptq8yg83vtulad30gpp4mhxue69uhkummn9ekx7mq...
Corny Chat caches notes and profiles for the session, updating periodically. It's main burden is the initial client download.