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Question 748 of 1,000

Design and plan a cloud solution architecture →hardMultiple ChoiceObjective-mapped

Google PCA Design and plan a cloud solution architecture Practice Question

This PCA practice question tests your understanding of design and plan a cloud solution architecture. 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.

Network Topology

Refer to the exhibit. An engineer is investigating why web-01 was removed from the load balancer target pool. What is the most likely root 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.

Network Topology

A
The firewall rule allowing traffic from web-01 to db-01 on port 3306 has been removed or misconfigured.
The timeout when connecting to the database suggests a firewall or network path issue blocking TCP/3306 traffic.
B
The database instance db-01 is running out of memory and rejecting connections.
Why wrong: Timeout suggests network-level issue, not resource exhaustion (which would typically produce a different error).
C
The load balancer health check is misconfigured to use an incorrect port.
Why wrong: The health check failure is a symptom, not the root cause; the underlying issue is the database connectivity.
D
The instance web-01 is running an outdated version of the web server software.
Why wrong: There is no evidence of outdated software; the logs point to a connectivity issue.

Full breakdown with real-world context →

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

✓

The firewall rule allowing traffic from web-01 to db-01 on port 3306 has been removed or misconfigured.

The exhibit shows that web-01 was removed from the load balancer target pool. In Google Cloud, a load balancer health check determines instance eligibility; if the health check fails, the instance is automatically removed. The most likely root cause is that the firewall rule allowing traffic from web-01 to db-01 on port 3306 has been removed or misconfigured, which would cause the health check (which often tests connectivity to a backend service like a database) to fail, leading to removal.

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 firewall rule allowing traffic from web-01 to db-01 on port 3306 has been removed or misconfigured.
Why this is correct
The timeout when connecting to the database suggests a firewall or network path issue blocking TCP/3306 traffic.
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 database instance db-01 is running out of memory and rejecting connections.
Why it's wrong here
Timeout suggests network-level issue, not resource exhaustion (which would typically produce a different error).
✗
The load balancer health check is misconfigured to use an incorrect port.
Why it's wrong here
The health check failure is a symptom, not the root cause; the underlying issue is the database connectivity.
✗
The instance web-01 is running an outdated version of the web server software.
Why it's wrong here
There is no evidence of outdated software; the logs point to a connectivity issue.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Google Cloud often tests the misconception that a database issue (like memory exhaustion) directly causes load balancer removal, but the real trigger is a health check failure due to a firewall rule blocking the health check probe.

Detailed technical explanation

How to think about this question

Google Cloud load balancers use health checks that send probes (e.g., HTTP, TCP, or SSL) to instances on a defined port and path. If the health check fails consecutively (default: 2 failures), the instance is marked unhealthy and removed from the target pool. A missing firewall rule for port 3306 would block the health check probe if it targets that port, causing removal. The health check configuration often includes a 'check interval' (default 5 seconds) and 'timeout' (default 5 seconds), and the firewall must allow traffic from the load balancer's health check source ranges (e.g., 35.191.0.0/16, 130.211.0.0/22) to the instance's health check port.

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 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

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.

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FAQ

Questions learners often ask

What does this PCA question test?

Design and plan a cloud solution architecture — This question tests Design and plan a cloud solution architecture — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The firewall rule allowing traffic from web-01 to db-01 on port 3306 has been removed or misconfigured. — The exhibit shows that web-01 was removed from the load balancer target pool. In Google Cloud, a load balancer health check determines instance eligibility; if the health check fails, the instance is automatically removed. The most likely root cause is that the firewall rule allowing traffic from web-01 to db-01 on port 3306 has been removed or misconfigured, which would cause the health check (which often tests connectivity to a backend service like a database) to fail, leading to removal.

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.

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