In the dynamic fields of DevOps and Site Reliability Engineering (SRE), effective monitoring is essential for maintaining robust systems, and this article explores three primary metrics frameworks — R.E.D., U.S.E., and the "Four Golden Signals." The R.E.D. framework, which focuses on Rate, Errors, and Duration, provides insight into the application's health by assessing request frequency, error rates, and latency. The U.S.E. framework targets infrastructure performance by examining Utilization, Saturation, and Errors, offering a snapshot of resource usage and potential bottlenecks. The "Four Golden Signals," introduced by Google, encompass Latency, Traffic, Errors, and Saturation, providing a comprehensive overview of system health to ensure optimal performance and user satisfaction. These frameworks, though distinct, can be combined to form a holistic monitoring strategy that proactively identifies and resolves issues, enhancing system reliability and performance. The article also suggests that these foundational metrics can support higher-level monitoring tasks, such as defining Service Level Objectives and managing infrastructure costs for product-led growth.