How many people are required to moderate a 3 billion member network? How do you decide the number? How many do you currently employ city/state/country wise. Si

How many people are required to moderate a 3 billion member network? How do you decide the number? How many do you currently employ city/state/country wise. Since the engagement algos/infinite scroll/like button/follower counts etc are meddling with the brains reward mechanisms, what determines such meddling is psychologically safe?