@grishka probably an update activity with the actor as an object.
I don't think that anyone exposes plain avatar images as activitypub addressable objects for which case you would receive an update for the avatar itself.
1. I receive a reply to a post of someone who I follow. So I fetch the actor object for whoever made the reply and store it in my database.2. The user who made the reply changes their avatar.3. I don't receive anything because no one on my instance follows that user.4. When I try to load the avatar using the URL I have stored, I get a 404 because it no longer exists.
Gregory's Server
@mariusor actually, here's my problem.
1. I receive a reply to a post of someone who I follow. So I fetch the actor object for whoever made the reply and store it in my database.2. The user who made the reply changes their avatar.3. I don't receive anything because no one on my instance follows that user.4. When I try to load the avatar using the URL I have stored, I get a 404 because it no longer exists.
How does everyone else solve this?