Google PCA Design and plan a cloud solution architecture Practice Question
A logistics company runs a latency-sensitive order-tracking service on Compute Engine instances spread across three zones in one region. They need the architecture to survive the loss of an entire zone while keeping inter-instance latency low, and they want automatic failover without manual intervention. Which design should the architects implement?
⚠ Common exam trap
The trap here is assuming a global load balancer provides zone resilience even when the backend instances all live in a single zone, where there is nothing to fail over to.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deploy a managed instance group with regional distribution across the three zones, front it with a regional external Application Load Balancer, and configure health checks with autoscaling.
Spreading a regional managed instance group across three zones means a zone outage only removes a fraction of capacity, and health-checked load balancing automatically diverts traffic from failed instances and restores it on recovery. This delivers unattended, in-region failover with low latency, unlike single-zone groups, unmanaged instances, or global routing that can add distance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Deploy a managed instance group in each of the three zones separately, and place a global external Application Load Balancer in front of all three groups.
Why it's wrong here
Three separate zonal managed instance groups can work, but the global external Application Load Balancer is designed for global traffic distribution and may route users to distant regions, adding latency for a regional latency-sensitive service. A single regional managed instance group with a regional load balancer is simpler and keeps traffic local, better matching the low-latency, in-region failover requirement.
- ✓
Deploy a managed instance group with regional distribution across the three zones, front it with a regional external Application Load Balancer, and configure health checks with autoscaling.
Why this is correct
A regional managed instance group spreads instances across zones, so losing one zone leaves capacity in the others. A regional load balancer with health checks automatically stops sending traffic to unhealthy instances and resumes when they recover, delivering unattended failover while keeping traffic within the region for low latency.
- ✗
Deploy standalone Compute Engine instances in each of the three zones with static external IPs and use DNS round-robin to distribute client traffic.
Why it's wrong here
Standalone instances are not managed as a group, so failed instances are not automatically recreated, and DNS round-robin cannot detect unhealthy endpoints or remove them quickly because of DNS caching. This design lacks automatic health-based failover and self-healing, so a zone loss would degrade service until manual intervention.
- ✗
Deploy a managed instance group in a single zone, front it with a global external Application Load Balancer, and rely on the load balancer to fail over across regions.
Why it's wrong here
A single-zone managed instance group has no capacity in other zones, so a zone outage takes the entire backend offline. A global load balancer can only fail over to backends that exist; with none in other zones, there is nothing to fail over to, and cross-region routing would also add latency contrary to the requirement.
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Key term
Compute Engine
Compute Engine is Google Cloud's Infrastructure-as-a-Service (IaaS) offering that lets you create and run virtual machines on Google's infrastructure.
Key term
Managed instance group
A managed instance group is a collection of identical virtual machine instances that are automatically managed as a single unit to ensure high availability and scalability.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Google Cloud exam blueprint
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