This document discusses service reliability monitoring strategies. It describes a service reliability hierarchy that focuses on preventing incidents rather than just responding to them. It also discusses using metrics and alerts to monitor services at different levels of granularity. Specifically, it recommends alerting on high-level service objectives while still allowing inspection of individual components. The document then provides examples of how AWS CloudWatch can be used to collect metrics, define alerts and monitor services. It also discusses the tradeoffs of white-box vs black-box monitoring approaches.