You are deploying a critical application on Compute Engine. The application requires high availability and must survive a zonal failure. You have created a managed instance group (MIG) with autoscaling across two zones. The application state is stored in a Cloud SQL instance with a read replica in another region. The application also uses a shared static IP address for client access. During a test, you simulate a failure of zone us-central1-a. You observe that the MIG automatically creates new instances in the remaining zone, but the application becomes unreachable for several minutes. What is the most likely cause of the downtime?
Trap 1: The static IP address was not configured to failover to the…
Static IP is not tied to a zone in this context.
Trap 2: The Cloud SQL read replica did not promote to primary quickly…
The read replica is for reads, not writes; the primary may not be affected.
Trap 3: The managed instance group's autoscaler took too long to create new…
MIGs typically create instances quickly.
- A
The load balancer's health check interval and timeout caused a delay in marking the backend instances as unhealthy and routing traffic to the new zone.
Health checks need time to detect failure and update routing.
- B
The static IP address was not configured to failover to the remaining zone.
Why wrong: Static IP is not tied to a zone in this context.
- C
The Cloud SQL read replica did not promote to primary quickly enough.
Why wrong: The read replica is for reads, not writes; the primary may not be affected.
- D
The managed instance group's autoscaler took too long to create new instances in the remaining zone.
Why wrong: MIGs typically create instances quickly.