Wouldn't you need to listen to EVERY kind 3 update, period? How else would it know whether an update to some npub's kind 3 was or was not adding your npub as a follow?
Discussion
you would create a filter {#p: your pubkey, kinds: 3} which would only get contact lists that you are on. Then you would have to keep state to not count duplicates
Got it, so then the relays would only serve up kind 3 requests that actually contain your npub, so your client doesn't have to look at every single kind 3 in existence each time it checks for follower updates, but it's still a massive amount of data to have to download every time it checks for updates, and that would need to be stored locally to avoid double-counting.
Yeah, not something that is realistic on a mobile client without a server that can do it off-device.
Thank you good sirs ! Appreciate your replies