Traffic Mirroring
Traffic mirroring, also known as traffic shadowing, provides a powerful way to bring changes to production at the lowest possible risk. The mirror sends a copy of real-time traffic to the mirroring service. Mirrored traffic goes outside of the critical request path of the main services.
In non-production or test environments, trying to access all possible combinations of test cases for a service is unrealistic. In some cases, the work of writing these test cases may not match actual production needs. In the ideal case, you can use real-time production use and traffic to help improve the functional regions you miss in the test environment.