Scale is something of a measure of popularity. If our API serves 234 million requests per day, then presumably we're running something pretty popular and widely

Scale is something of a measure of popularity. If our API serves 234 million requests per day, then presumably we're running something pretty popular and widely known. Because of the democratization of "big data" and the (relatively) recent uptick in large internet services, serious scale is an engineering challenge that a few have been tackling for awhile, but many are facing for the first time. Think any company that has recently realized their data needs are bigger than what Excel can handle.