@mariusor just to be clear. I don't have c2s and I don't plan to because it makes any semblance of a good client app impossible anyway. I treat my s2s ActivityPub inbox more like an API endpoint, and don't store the activities themselves — I instead apply them to my local state.
@grishka then it seems to me that you're not actually asking questions about activitypub. I feel like you can apply my reply above no matter what your actual storage layout is.