Network and performance
How much bandwidth a node uses, what it stores, and what it costs to keep somebody else's world alive.
Two shapes of traffic, and they are worth telling apart. A world's whole archive is a cold bootstrap for a peer that has nothing at all: it is seeded when the world is shared, again when the server stops, and otherwise on a slow cadence. Live change does not ride it — committed region snapshots go to the worker as they happen, which moves the chunks that changed rather than the world that contains them.
Copies are whole rather than fragmented, and how many the network keeps is arithmetic over how often a home machine is switched on, capped by the number of peers that exist.