Gedalyah Reback's article explores the distinct roles and capabilities of Prometheus and Nagios in infrastructure monitoring, highlighting the importance of metrics like mean-time-to-detect (MTTD) and mean-time-to-repair (MTTR) for SaaS companies. Prometheus is praised for its ease of integration and use in monitoring application functionality, with features like a built-in database, PromQL query language, and compatibility with visualization tools like Grafana. In contrast, Nagios excels in monitoring application networks and security, offering multiple products like Nagios XI, Log Server, Network Analyzer, and Fusion, each tailored to specific monitoring needs. Prometheus is noted for its extensive open-source community support and flexibility, while Nagios is commended for its scalability and customization capabilities. Despite their differences, the article suggests that using both tools together could provide a more comprehensive monitoring solution for DevOps teams, as demonstrated by Runtastic's migration from Nagios to Prometheus due to configuration challenges and false positive alerts.