Keep in mind that the systems required depend on the actual tasks, not just whether you can fit the data on a disk. I don't think the FB Newsfeed (show more pho

Keep in mind that the systems required depend on the actual tasks, not just whether you can fit the data on a disk. I don't think the FB Newsfeed (show more photos from your cousin because you liked their text post last week...) can be built using only SQL.