This is the related PR: https://github.com/laravel/framework/pull/49695

Apparently it uses Window Functions (supported in most modern databases):

select * from (
  select *, row_number() over (partition by "user_id" order by "created_at" desc) as row_num
  from "posts"
  where "posts"."user_id" in (1, 2, 3)
) as temp_table
where row_num <= 5
order by row_num

So I guess I'll be able to replace my manual code:

Post::select([
    DB::raw('ROW_NUMBER() OVER (PARTITION BY user_id ORDER BY created_at DESC) AS row_num'),
    // ...
])
->where('row_num', '<=', 3);

I wish that kind of info was explained in the video. I love Laracasts but I'm learning less and less from the platform as I get more experience. The videos are very similar to the ones from Lavavel News, the Laravel YouTube channel, etc. I know it might feel overwhelming to new developers but for everybody else this is where the value is.

Limitless Limits for Eager Loading