How did you understand that the service was working correctly?

To understand the correct operation of the service, I usually use several approaches:

• Metrics monitoring: I track key indicators (for example, response time, error count, load) using monitoring systems (Prometheus, Grafana).
• Logs: I analyze logs for errors and anomalies.
• Automated tests: I ensure that integration and e2e tests are in place and run regularly.
• Business logic check: I verify that the service performs its functions according to requirements.
• Health checks: The service should provide endpoints for status checks that can be polled.

For example, if the service is a web application, I check that HTTP requests are processed correctly, there are no 5xx errors, and metrics show stable operation without sharp jumps.