This may be of interest:

The Gossip Model was named after this client, because gossip never used a simple list of relays. From day one it tried to find posts of people that you follow wherever they are most likely to be, based on those people's relay lists as well as half a dozen other heuristics. Today multiple clients use a similar model, focused around (NIP-65). Gossip connects to all relays necessary to cover everybody you follow, while also trying to listen to the minimum number of relays necessary to do that (considering that there is overlap, and that people generally post to multiple relays). It also dynamically adjusts to relays being down or disconnecting.