Comment by autoexec

> More likely it is the inverse: Selecting a random video at scale is the costly problem.

if that feature existed it would never be a random video from all the available videos. It'd be a random-seeming video from a carefully curated selection of videos that youtube wants to push at certain users, and in some cases were paid to promote. Users wouldn't know and wouldn't care anyway because they pushed a button and got content without thinking.