A small number of API requests to your microservices-based application take a very long time. You know that each request to the API can traverse many services. You want to know which service takes the longest in those cases. What should you do?

The problem describes long-running requests traversing multiple microservices, and the goal is to identify which specific service is causing the delay. Stackdriver Trace (now Cloud Trace) is designed precisely for this purpose: it provides distributed tracing, allowing you to visualize the end-to-end latency of a request across all services it touches and pinpoint bottlenecks within individual services. Setting timeouts would only fail requests faster, not identify the slow service. Sending custom metrics to Stackdriver Monitoring could show overall latency but wouldn't break down the latency per service. Stackdriver Monitoring insights might show high latency periods but wouldn't provide the granular, per-service breakdown that tracing offers.