Google PCA Manage and provision cloud infrastructure Practice Question
This PCA practice question tests your understanding of manage and provision cloud infrastructure. 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 company runs a critical web application behind an external HTTPS load balancer. The backend consists of a managed instance group of Compute Engine instances. Users report intermittent 502 Bad Gateway errors. The load balancer logs show occasional health check failures for some instances. The instances have a custom health check endpoint that returns a 200 status code only if the application is fully healthy. The application logs do not show any errors, and CPU/memory usage on the instances is normal. What should be the first troubleshooting step to identify the root cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check the application's logs on the instances to see why the health check endpoint sometimes returns non-200
Option B is correct. The health check is failing, and since the instances show normal CPU/memory, the application might be slow to respond under certain conditions. Checking the application logs on the instances will reveal why the health check endpoint returns non-200. Option A is wrong because increasing the interval doesn't fix the underlying issue. Option C is wrong because adding instances won't help if the health check is flaky. Option D is wrong because TCP health check would not validate application health and could mask the problem.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Change the health check to a TCP check on the application's port
Why it's wrong here
TCP check does not verify application health; would not catch issues.
✗
Increase the health check check interval and decrease the unhealthy threshold
Why it's wrong here
This only masks the problem, not solves it.
✗
Increase the number of instances in the managed instance group
Why it's wrong here
Does not address why health check fails.
✓
Check the application's logs on the instances to see why the health check endpoint sometimes returns non-200
Why this is correct
This directly investigates the health check failure.
Clue confirmation
The clue word "first" in the question point toward this answer.
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PCA subnetting questions on CIDR, address ranges, and subnet selection.
Manage and provision cloud infrastructure — This question tests Manage and provision cloud infrastructure — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Check the application's logs on the instances to see why the health check endpoint sometimes returns non-200 — Option B is correct. The health check is failing, and since the instances show normal CPU/memory, the application might be slow to respond under certain conditions. Checking the application logs on the instances will reveal why the health check endpoint returns non-200. Option A is wrong because increasing the interval doesn't fix the underlying issue. Option C is wrong because adding instances won't help if the health check is flaky. Option D is wrong because TCP health check would not validate application health and could mask the problem.
What should I do if I get this PCA question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PCA subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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