rate - error rate - proportion of service errors - traffic / system throughput - typically measured in requests per second - availability - what’s the uptime of a service - saturation - measures the system fraction, emphasizing the resources that are most constrained (e.g., in a memory-constrained system, show memory; in an I/O-constrained system, show I/O). I experienced system degrading service levels before being saturated, e.g. 90% CPU utilization triggered a service degradation already. Guidance - The Four Golden Signals Addressing the most frequent pitfalls when transitioning to Microservices - 2020 12 08 - Magnus Kulke/Lothar Schulz SRE Book - The Four Golden Signals