In the service flow, which metric reflects the overall performance of called services?

The metric that reflects the overall performance of called services is the average time spent in services. This metric is crucial because it provides insight into how long each call to a service takes to complete. By analyzing this average time, one can assess the efficiency and speed of the service's response to requests. A longer average time can indicate potential bottlenecks or performance issues, while a shorter time suggests that the service is performing well.

This metric is particularly valuable for optimizing service performance, as it helps identify areas for improvement. It allows teams to evaluate and compare the performance of different services and make informed decisions on where to apply optimizations or further investigate issues.

Other metrics, while important, do not focus solely on the performance aspect of the services. For example, requests details provide information about the volume and characteristics of requests but do not directly reflect performance. Similarly, service instances indicate how many instances of a service are running, and error rates focus on the reliability aspect rather than the performance of service calls.