When does the multiplication happen?

Somebody has to combine "one author" with "many readers". Choose where.

System so far· 6 parts

Select a component to see what it is responsible for and which state it owns.

What you need to know

0 of 2 checks done

The two strategies:
Fan-out on write (push) Fan-out on read (pull)
Posting insert into every follower's list store the post once
Reading fetch one list fetch every followed account's posts, merge
Cost lands on writes reads
Work it out
With pull, each of 300,000 reads a second fetches recent posts from the ~200 accounts its reader follows. About how many lookups a second is that?
Your estimatelookups per second
?
Check
Timelines could hold full copies of posts or just post IDs. What happens to copies when the author deletes a post?

	Fan-out on write (push)	Fan-out on read (pull)
Posting	insert into every follower's list	store the post once
Reading	fetch one list	fetch every followed account's posts, merge
Cost lands on	writes	reads