The answer is to use a multi-zone deployment with a regional managed instance group and a global load balancer. This strategy ensures high availability for a Compute Engine instance group by distributing instances across multiple zones within a single region, so if one zone fails, the regional MIG automatically heals by recreating instances in healthy zones. The global load balancer then routes traffic only to those healthy instances, making the stateless web application resilient to zonal outages without manual intervention. On the Google Professional Cloud Developer exam, this tests your understanding of regional versus zonal resources and the distinction between automatic healing and load balancing health checks. A common trap is choosing a zonal MIG with a regional load balancer, which still leaves a single point of failure at the zone level. Remember the memory tip: “Regional MIGs survive zone failure; zonal MIGs do not.”
PCD Practice Question: Designing highly scalable, available, and reliable cloud-native applications
This PCD practice question tests your understanding of designing highly scalable, available, and reliable cloud-native applications. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which two strategies should be implemented to ensure high availability for a Compute Engine instance group running a stateless web application?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use regional managed instance group
Regional managed instance groups (MIGs) distribute instances across multiple zones within a region, providing automatic healing and high availability by recovering from zone failures. Combined with a global load balancer, they ensure traffic is routed only to healthy instances, making them ideal for stateless web applications that require resilience against zonal outages.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use preemptible VMs
Why it's wrong here
Preemptible VMs can terminate at any time and are not suitable for HA.
✓
Use regional managed instance group
Why this is correct
Regional MIG distributes instances across zones for automatic failover.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use global load balancing
Why it's wrong here
Global LB provides traffic distribution but does not by itself make the instance group highly available.
✗
Use instance templates
Why it's wrong here
Instance templates define the instance configuration but do not affect availability.
✓
Use multi-zone deployment
Why this is correct
Deploying across zones protects against zone failure.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that global load balancing alone provides high availability, but it only distributes traffic; the underlying compute resources must be resilient, which requires a regional MIG or multi-zone deployment to survive zone failures.
Detailed technical explanation
How to think about this question
Regional managed instance groups use autoscaling and health checks to automatically replace failed instances across multiple zones, leveraging the fact that each zone has independent failure domains. Under the hood, the MIG controller monitors instance health via HTTP, TCP, or SSL health probes and performs rolling updates or canary deployments without downtime. In a real-world scenario, if a zone experiences a network partition, the global load balancer's anycast IP (e.g., 34.120.0.0/16) routes traffic only to healthy instances in remaining zones, ensuring the application remains available.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Designing highly scalable, available, and reliable cloud-native applications — This question tests Designing highly scalable, available, and reliable cloud-native applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use regional managed instance group — Regional managed instance groups (MIGs) distribute instances across multiple zones within a region, providing automatic healing and high availability by recovering from zone failures. Combined with a global load balancer, they ensure traffic is routed only to healthy instances, making them ideal for stateless web applications that require resilience against zonal outages.
What should I do if I get this PCD question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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