The right way would be to use activitypub to query the followers collection of the actor and display that instead of relying on local out-of-date caches.
Do it too often and you're wasting bandwidth and CPU time on both instances. Do that too rarely and your data is outdated af. Especially important for collections because that's potentially hundreds of requests, all to find out someone has one new follower.
Gregory's Server
@mariusor @liaizon the problem with actively querying something from other instances is that you never know when to do that. See https://socialhub.activitypub.rocks/t/avatar-updates-for-users-who-arent-followed-by-anyone/384
Do it too often and you're wasting bandwidth and CPU time on both instances. Do that too rarely and your data is outdated af. Especially important for collections because that's potentially hundreds of requests, all to find out someone has one new follower.