The book describes data-driven approach to optimal monitoring and alerting in distributed computer systems. It interprets monitoring as a continuous process aimed at extraction of meaning from system's data. The resulting wisdom drives effective maintenance and fast recovery - the bread and butter of web operations. The content of the book gives a scalable perspective on the following topics: anatomy of monitoring and alerting conclusive interpretation of time series data-driven approach to setting up monitors addressing system failures by their impact applications of monitoring in automation reporting on quality with quantitative means and more!