- A
A VPC firewall rule blocking traffic to the VM
Why wrong: Firewall rules are static and would block traffic to all instances equally — they don't dynamically respond to application health.
- B
An HTTP health check configured on the backend service
HTTP health checks probe the application port. A crashed application fails the probe, causing the load balancer to stop directing traffic to that VM until it recovers.
- C
A Cloud Armor security policy blocking the crashed instance's IP
Why wrong: Cloud Armor applies rules to incoming requests from external clients — it doesn't monitor backend instance health.
- D
The instance group autoscaling policy detecting the failure
Why wrong: Autoscaling adjusts instance count based on metrics — it doesn't directly control load balancer routing per instance health.
Quick Answer
The answer is an HTTP health check configured on the backend service. This is correct because the Google Cloud load balancer relies on application-layer health probes, not just VM status; when the application process crashes, the VM remains running but the health check fails—returning a non-2xx status code or timing out—so the load balancer automatically stops routing new traffic to that unhealthy instance. On the Google Associate Cloud Engineer exam, this tests your understanding that health checks operate at the application level, not the infrastructure level, and a common trap is assuming the load balancer detects crashes via VM instance state alone. Remember: a running VM with a dead app is still “unhealthy” to the load balancer. Memory tip: think “HTTP 200 or no traffic”—if the app doesn’t respond with a 2xx, the load balancer cuts it off.
Google ACE Practice Question: Ensuring successful operation of a cloud solution
This ACE practice question tests your understanding of ensuring successful operation of a cloud solution. 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.
A load balancer is routing traffic to a VM where the application process has crashed, but the VM itself is still running. What prevents the load balancer from continuing to send traffic to this instance?
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
An HTTP health check configured on the backend service
The load balancer uses an HTTP health check to periodically probe the application on the VM. When the application process crashes, the health check fails (e.g., returns a non-2xx status code or times out), and the load balancer automatically stops routing new traffic to that unhealthy instance. This is the standard mechanism in Google Cloud for detecting application-level failures, as opposed to infrastructure-level failures.
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.
- ✗
A VPC firewall rule blocking traffic to the VM
Why it's wrong here
Firewall rules are static and would block traffic to all instances equally — they don't dynamically respond to application health.
- ✓
An HTTP health check configured on the backend service
Why this is correct
HTTP health checks probe the application port. A crashed application fails the probe, causing the load balancer to stop directing traffic to that VM until it recovers.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
A Cloud Armor security policy blocking the crashed instance's IP
Why it's wrong here
Cloud Armor applies rules to incoming requests from external clients — it doesn't monitor backend instance health.
- ✗
The instance group autoscaling policy detecting the failure
Why it's wrong here
Autoscaling adjusts instance count based on metrics — it doesn't directly control load balancer routing per instance health.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse infrastructure-level health (VM running) with application-level health (process responding), and assume autoscaling or firewall rules handle this, when in fact only a properly configured health check can detect a crashed application process.
Detailed technical explanation
How to think about this question
Google Cloud HTTP(S) load balancers use configurable health checks that send requests to a specified path (e.g., /health) on a defined interval (default 5 seconds). If the health check fails consecutively (default 2 failures), the instance is marked unhealthy and removed from the load balancer's backend pool. The health check can be customized with timeouts, thresholds, and response codes, and it operates at the application layer (HTTP/HTTPS), making it ideal for detecting crashes in the application process itself.
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.
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FAQ
Questions learners often ask
What does this ACE question test?
Ensuring successful operation of a cloud solution — This question tests Ensuring successful operation of a cloud solution — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: An HTTP health check configured on the backend service — The load balancer uses an HTTP health check to periodically probe the application on the VM. When the application process crashes, the health check fails (e.g., returns a non-2xx status code or times out), and the load balancer automatically stops routing new traffic to that unhealthy instance. This is the standard mechanism in Google Cloud for detecting application-level failures, as opposed to infrastructure-level failures.
What should I do if I get this ACE 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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Last reviewed: Jun 11, 2026
This ACE 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 ACE exam.
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