Your customer wants to do resilience testing of their authentication layer. This consists of a regional managed instance group serving a public REST API that reads from and writes to a Cloud SQL instance. What should you do?

The customer wants to test the resilience of their authentication layer. Shutting off all VMs in a zone directly simulates a zonal outage, which is a critical resilience test for a regional managed instance group. This allows you to observe how the application handles such a failure, including automatic failover and recovery mechanisms, and whether the authentication layer remains available. Engaging a security company for web scraping is a security monitoring activity, not a resilience test. Deploying intrusion detection software is also a security measure, focused on detecting unauthorized access, not on testing system resilience to outages. Configuring a read replica and triggering failover tests Cloud SQL resilience, but the question specifically asks about the authentication layer served by the managed instance group, which is best tested by simulating an outage of its compute resources.