The correct choice is to create a managed instance group using an instance template based on instance-3's boot disk. This works because a managed instance group (MIG) provides automated health checking and auto-healing, meaning if instance-3 fails, the MIG will automatically recreate it from the template, restoring the instance quickly without manual intervention. On the Google Professional Cloud Developer exam, this scenario tests your understanding of designing resilient, highly available applications using MIGs and instance templates—a core concept for the "Deploying and Implementing" section. A common trap is to assume a simple backup or snapshot suffices, but those require manual restoration steps, whereas a MIG handles failure recovery instantly. Remember the key difference: snapshots are for data recovery, but instance templates in a MIG are for rapid instance replacement. Memory tip: "MIG auto-heals, snapshots just reveal."
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. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit
Refer to the exhibit.
gcloud compute instances list --format='table(name, zone, status, machineType, scheduling.preemptible)'
NAME ZONE STATUS MACHINE_TYPE PREEMPTIBLE
instance-1 us-central1-a RUNNING n1-standard-1 false
instance-2 us-central1-b RUNNING n1-standard-2 false
instance-3 us-central1-a TERMINATED n1-standard-1 false
instance-4 us-central1-c RUNNING n1-standard-1 true
A developer runs the command shown in the exhibit. They need to ensure that the application running on instance-3 can be restored quickly if it fails. What should they do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a managed instance group using an instance template based on instance-3's boot disk.
Option C is correct because a managed instance group (MIG) with an instance template based on instance-3's boot disk provides automated health checking, auto-healing, and managed instance replacement. If instance-3 fails, the MIG automatically recreates it from the template, ensuring rapid restoration without manual intervention. This aligns with the goal of designing highly available and reliable applications on Google Cloud.
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.
✗
Add instance-3 to an unmanaged instance group.
Why it's wrong here
Unmanaged instance groups do not provide auto-healing.
✗
Configure Cloud DNS with a health check pointing to instance-3.
Why it's wrong here
DNS does not manage instance health or recreation.
✓
Create a managed instance group using an instance template based on instance-3's boot disk.
Why this is correct
Managed instance groups automatically recreate failed instances.
Related concept
Read the scenario before looking for a memorised answer.
✗
Take a snapshot of instance-3's disk and use it to create a new instance manually.
Why it's wrong here
Manual restore is slower than auto-healing.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between health-check-based traffic routing (Cloud DNS) and health-check-based instance recovery (MIG auto-healing), leading candidates to confuse DNS failover with automated instance restoration.
Detailed technical explanation
How to think about this question
A managed instance group uses an instance template to define the machine configuration, boot disk image, and metadata for all instances in the group. When an instance fails a health check (e.g., TCP or HTTP health probes), the MIG's auto-healing feature automatically deletes the unhealthy instance and creates a new one from the template, typically within minutes. Under the hood, the MIG uses the Compute Engine Instance Group Manager (IGM) to monitor instance health via configurable health checks and maintain the desired instance count, ensuring rapid recovery without manual snapshot or disk operations.
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
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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: Create a managed instance group using an instance template based on instance-3's boot disk. — Option C is correct because a managed instance group (MIG) with an instance template based on instance-3's boot disk provides automated health checking, auto-healing, and managed instance replacement. If instance-3 fails, the MIG automatically recreates it from the template, ensuring rapid restoration without manual intervention. This aligns with the goal of designing highly available and reliable applications on Google Cloud.
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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