Quick Answer
The answer is the load balancer logs with the type 'loadbalancing.googleapis.com'. These logs capture every health check probe result, including the probe source IP, target instance, response code, and latency, which is exactly what you need to diagnose intermittent failures. On the Google Professional Cloud DevOps Engineer exam, this tests your understanding of how Cloud Load Balancing integrates with Cloud Logging to surface health check data—a common trap is confusing these logs with instance-level logs or VPC flow logs, which lack probe-specific details. A strong memory tip is to think of the load balancer as the orchestrator: it sends probes, and its own logs are the single source of truth for those results, not the backend instances. Remember the mnemonic "LBL for HCP" (Load Balancer Logs for Health Check Probes) to quickly recall the correct log view when troubleshooting routing anomalies.
This PCDOE practice question tests your understanding of implementing service monitoring strategies. 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.
An e-commerce platform is using Cloud Load Balancing with a backend service that has a custom health check. The health check is failing intermittently, causing traffic to be routed away from healthy instances. The team has enabled Cloud Logging and wants to diagnose the issue. Which log view should they examine to see the health check probe results?
VPC flow logs
Why wrong: VPC flow logs show packet-level traffic, not health check results.
Cloud Audit Logs (Admin Activity)
Why wrong: Audit logs track administrative actions, not health checks.
Instance serial port output logs
Why wrong: Serial port logs show OS-level boot and console messages.
Load balancer logs (type: 'loadbalancing.googleapis.com')
Load balancer logs contain health check probe results.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Load balancer logs (type: 'loadbalancing.googleapis.com')
Load balancer logs (type: 'loadbalancing.googleapis.com') contain detailed records of health check probes, including the probe source IP, target instance, response code, and latency. This is the exact log view that captures health check probe results, enabling the team to identify intermittent failures by correlating probe timestamps with instance health status changes.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
VPC flow logs
Why it's wrong here
VPC flow logs show packet-level traffic, not health check results.
Cloud Audit Logs (Admin Activity)
Why it's wrong here
Audit logs track administrative actions, not health checks.
Instance serial port output logs
Why it's wrong here
Serial port logs show OS-level boot and console messages.
Load balancer logs (type: 'loadbalancing.googleapis.com')
Why this is correct
Load balancer logs contain health check probe results.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates confuse VPC flow logs (which show network-level traffic) with load balancer logs (which show application-level health check results), or assume that audit logs or serial console logs would contain runtime health check data.
Trap categories for this question
Command / output trap
VPC flow logs show packet-level traffic, not health check results.
Detailed technical explanation
Health check probes are sent from Google's health check systems (IP ranges like 35.191.0.0/16 and 130.211.0.0/22) to backend instances. The load balancer logs record each probe's HTTP response code, round-trip time, and whether the instance passed or failed; intermittent failures often stem from timeouts due to high CPU or slow application responses, which can be diagnosed by analyzing probe latency trends in these logs.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
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FAQ
Implementing service monitoring strategies — This question tests Implementing service monitoring strategies — Read the scenario before looking for a memorised answer..
The correct answer is: Load balancer logs (type: 'loadbalancing.googleapis.com') — Load balancer logs (type: 'loadbalancing.googleapis.com') contain detailed records of health check probes, including the probe source IP, target instance, response code, and latency. This is the exact log view that captures health check probe results, enabling the team to identify intermittent failures by correlating probe timestamps with instance health status changes.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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.
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