Golden signals in application monitoring are a set of key performance indicators (KPIs) that provide a comprehensive view of an application’s health and performance. These signals are crucial for ensuring that an application meets its service level objectives (SLOs) and delivers a satisfactory user experience. Golden signals help teams quickly identify and respond to issues, ultimately improving system reliability and user satisfaction. The four primary golden signals are:

1. Latency: Latency measures the time it takes for a request to travel from the user’s device to the application and back. It’s a critical metric because users expect applications to respond quickly. High latency can indicate bottlenecks or performance problems within the application, its dependencies, or the network. Monitoring latency helps identify and address performance issues before they impact the user experience.
2. Error Rate: Error rate measures the percentage of requests that result in errors or failures. This includes HTTP 5xx status codes, database query failures, or any other unexpected errors. A high error rate can indicate issues with application code, infrastructure, or third-party services. Monitoring error rates helps teams identify and fix bugs or infrastructure problems promptly.
3. Traffic: Traffic refers to the volume of requests or transactions processed by the application. Monitoring traffic helps teams understand how the application’s load varies over time. Sudden spikes in traffic can lead to performance problems or outages if the application isn’t scaled appropriately. Additionally, understanding traffic patterns can inform capacity planning and resource allocation.
4. Saturation: Saturation measures the resource utilization of the application and its underlying infrastructure. It includes metrics like CPU usage, memory usage, and disk I/O. Monitoring saturation helps teams ensure that the application and its dependencies have enough resources to handle the current load. High saturation levels can lead to performance degradation or outages if resources become exhausted.