Best way to model data for a user's feed

Hi, I’m trying to figure out the best way to model data for a feed. Users can follow each other, and a user’s feed is a collection of posts/updates from the users they follow.

Suppose User A follows Users B, C, and D, and suppose we have the following updates:

  1. Time 1: User D updates profile picture.
  2. Time 2: User C posts a new video.
  3. Time 3: User D posts a new picture.
  4. Time 4: User B posts a new picture.

I have a collection keeping track of the event when each user follows another user (instead of storing an array of followers/following).

{
    _id: ObjectId(),
    followed_userID: userC,
    follower_userID: userA,
    timestamp: someTimestamp,
}

It’s easy to extract the list of followers/following by having a indexes on the timestamp & followed_userID and timestamp & follower_userID fields.

If User A wants to view their own feed, what kind of data model should I adopt to be able to get the most recent events from User A’s list of followers.

The naive way would be to get the entire array of users User A follows, and then iterate over each one to get their most recent posts, but this is clearly highly inefficient.

How should I be going about this?