relays are not supposed to store ephemerals at all, they either go out if someone is listening, or go into the void, the point of them is precisely ...
makes me think of something... there is overlap between post office protocol and publish-subscribe pattern, in that you can publish to an inbox, which can then be read by an eligible user. ephemeral events are kinda more like a one-to-many rendezvous relay pattern. almost, actually, the most specific element of the protocol that makes the name "relay" valid at all, because relay doesn't imply storage. that's a post office.