The Unofficial Google Data Science Blogby CHRIS HAULK It is sometimes useful to think of a large-scale online system ( LSOS ) as an abstract system with parameters $X$ affecting responses $Y$. Here, $X$ is a vector of tuning parameters that control the system's operating characteristics (e.g. the weight given to Likes in our video recommendation algorithm) while $Y$ is a vector of outcome measures such as different metrics of user expe
