Most "decentralized" networks end up with three servers in a rack and call it federation. The engineering hard problems aren't the protocol — they're onboarding, discovery, and trust. Here's what I learned building one. First principle: every node must be able to run without any central service. If your DNS goes down, can Alice still reach Bob? If the index dies, can a new node ever be found? Second: the user never thinks about federation. They type an address, see a name, send a message. The network topology is invisible.