I am making an app, that uses Instagram data to create some kind of rating of user profiles and their posts. My app periodically add new like/comment count with timestamp for stored posts in db and check profiles for new posts to add them in database.
Database schema for posts updates table:
id, post_id, user_id, likes_count, comments_count, timestamp
Nothing wrong with what you have done. It is efficient just set default values of zero for the likes_count and comments_count fields others not null.