Those are the best questions and the best answer is, "It's complex.". We've not answered of those problems in the ways you've hinted at though. Maybe one day t

Those are the best questions and the best answer is, "It's complex.". We've not answered of those problems in the ways you've hinted at though. Maybe one day there will be a High Scalability article that explains it... it takes more space than a HN comment would provide.