PCDOE Managing service incidents Practice Question
This PCDOE practice question tests your understanding of managing service incidents. 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 DevOps engineer is troubleshooting a production incident where users are getting 502 errors from a Google Cloud HTTP(S) Load Balancer. The backend service is a GKE deployment. Initial checks show the backend pods are healthy and responding. 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 load balancer's health check is failing on the backend instance group due to mismatch between health check port and backend port.
A 502 error from an HTTP(S) Load Balancer indicates that the load balancer is unable to establish a successful connection to the backend. Even though the backend pods are healthy and responding, the load balancer's health check may be failing because it is configured to check a different port (e.g., the health check port) than the port the backend service is actually serving traffic on (e.g., the backend port). This mismatch causes the load balancer to mark the backend instances as unhealthy, resulting in 502 errors for users.
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 load balancer's health check is failing on the backend instance group due to mismatch between health check port and backend port.
Why this is correct
502 errors indicate the backend is unhealthy to the load balancer.
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 backend pods are out of memory and crashing.
Why it's wrong here
Pods would be unhealthy, contradicting the scenario.
✗
The IAM permissions for the load balancer service account are misconfigured.
Why it's wrong here
Would cause 403 errors, not 502.
✗
The backend service has been accidentally deleted by another engineer.
Why it's wrong here
Would cause 'connection refused' errors, not 502.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between backend health and health check configuration, where candidates assume that if pods are healthy, the load balancer must also see them as healthy, ignoring the port mismatch or firewall rules that block health check probes.
Trap categories for this question
Scenario analysis trap
Pods would be unhealthy, contradicting the scenario.
Detailed technical explanation
How to think about this question
The HTTP(S) Load Balancer uses a health check probe to determine backend instance health; if the health check port (e.g., 8080) differs from the backend service port (e.g., 80), the health check may fail even though the application on the backend port is healthy. This is a common misconfiguration in GKE where the container's readiness probe port may not match the load balancer's health check port, leading to the load balancer draining traffic from healthy pods. In GCP, the health check is sent from the load balancer's health check system (source IPs in the 130.211.0.0/22 and 35.191.0.0/16 ranges) and must be allowed by the pod's network policy.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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.
Managing service incidents — This question tests Managing service incidents — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The load balancer's health check is failing on the backend instance group due to mismatch between health check port and backend port. — A 502 error from an HTTP(S) Load Balancer indicates that the load balancer is unable to establish a successful connection to the backend. Even though the backend pods are healthy and responding, the load balancer's health check may be failing because it is configured to check a different port (e.g., the health check port) than the port the backend service is actually serving traffic on (e.g., the backend port). This mismatch causes the load balancer to mark the backend instances as unhealthy, resulting in 502 errors for users.
What should I do if I get this PCDOE 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.
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This PCDOE 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 PCDOE exam.
Question Discussion
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