Which scheme for the formation of the event feed should I choose?

Question

Database

I read about the schemes for the formation of tapes and found only 2.
First: the formation of a common tape and pulling events from it to form a personal one.
Second: This is when a personal tape is created for each user. That is, at the moment when a person posts something, a list of all his subscribers is taken and this event is placed in each of his personal feeds.
Of these two schemes, everyone recommends using the second one, but one thing annoys me: if, for example, take 100k users who have 200 friends each, create 1 event per day, this turns out to be 20 million write requests to the database per day ( and this is only with 100k events). How to be in such situations (I understand about premature optimization, etc., but I'm just curious)? Or do you need to do things differently?

Answer 1

https://www.youtube.com/watch?v=KmIE5K6adus
watch all three parts. There are details about the tapes. It will bring in any case thoughts.