The answer is that a misconfigured autohealing health check is the most likely cause. In a managed instance group, autohealing depends entirely on a health check to determine instance status; if the health check specifies the wrong port, path, or protocol, the MIG will never mark instances as unhealthy, so it will not trigger replacement even during a traffic spike. This scenario tests your understanding of how Compute Engine separates autoscaling from autohealing—autoscaling adds instances based on load, but autohealing replaces only those the health check explicitly flags as failing. On the Google Professional Cloud Architect exam, a common trap is confusing autoscaling metrics with health check logic; remember that a MIG can scale up perfectly while unhealthy instances remain untouched if the health check is misconfigured. A useful memory tip: “Health check rules the replacement—if it’s wrong, the MIG stays strong.”
Google PCA Ensure solution and operations reliability Practice Question
This PCA practice question tests your understanding of ensure solution and operations reliability. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
A company runs a critical application on Compute Engine instances in a managed instance group (MIG) with autoscaling. During a traffic spike, some instances become unhealthy but are not automatically replaced. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The autohealing health check is misconfigured.
The most likely cause is that the autohealing health check is misconfigured. In a managed instance group, autohealing relies on a health check to detect unhealthy instances and trigger replacement. If the health check is misconfigured (e.g., wrong port, path, or protocol), the MIG will not recognize instances as unhealthy and will not automatically replace them, even during a traffic spike.
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.
✗
The MIG is regional and one zone failed.
Why it's wrong here
Regional MIGs automatically redistribute instances across zones; a single zone failure would cause instance recreation in other zones.
✓
The autohealing health check is misconfigured.
Why this is correct
MIG autohealing relies on a health check to detect unhealthy instances and replace them; a misconfiguration prevents detection.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The instance template has a startup script error.
Why it's wrong here
A startup script error would cause instances to never become healthy but would not prevent replacement of already unhealthy instances.
✗
The HTTP load balancer's health check is failing.
Why it's wrong here
The load balancer health check determines traffic routing, not instance replacement by the MIG.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between the MIG's autohealing health check and the load balancer's health check, leading candidates to incorrectly attribute instance replacement failures to load balancer issues rather than the MIG's own health check configuration.
Detailed technical explanation
How to think about this question
Autohealing in a MIG uses a separate health check resource (e.g., HTTP, HTTPS, TCP, or SSL) that must be explicitly attached to the group. The health check probes instances at a configurable interval (default 5 seconds) and timeout (default 5 seconds); if an instance fails a consecutive number of checks (default 2), it is marked unhealthy and replaced. A common misconfiguration is setting the health check to a path that does not exist on the instance or using an incorrect protocol, causing the MIG to never receive a healthy response and thus never trigger replacement.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this PCA question in full detail.
Ensure solution and operations reliability — This question tests Ensure solution and operations reliability — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The autohealing health check is misconfigured. — The most likely cause is that the autohealing health check is misconfigured. In a managed instance group, autohealing relies on a health check to detect unhealthy instances and trigger replacement. If the health check is misconfigured (e.g., wrong port, path, or protocol), the MIG will not recognize instances as unhealthy and will not automatically replace them, even during a traffic spike.
What should I do if I get this PCA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This PCA practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCA exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.