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Manage implementation of cloud architecture →hardMultiple ChoiceObjective-mapped

Google PCA Manage implementation of cloud architecture Practice Question

This PCA practice question tests your understanding of manage implementation of cloud 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.

A company runs multiple microservices on Cloud Run. Each service uses a Serverless VPC Access connector to connect to a shared Cloud Memorystore for Redis instance (standard tier) in a VPC network. The Redis instance is configured with a firewall rule that allows TCP connections on port 6379 from the VPC connector's subnet (10.8.0.0/28). After a recent code update, the order-service fails to connect to Redis, while the user-service continues to work. The error logs in order-service show 'connection refused'. The engineer verifies that both services use the same VPC connector, the same Redis instance IP, and the same service account. The VPC connector's metrics show no errors. 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.

Question 1hardmultiple choice

Review the full subnetting walkthrough →

A
The order-service is deployed in a different region than the Redis instance.
Why wrong: The order-service uses the same VPC connector as user-service and was working before; region mismatch would have caused issues from the start.
B
The order-service code now attempts to connect to Redis on port 6380.
A port mismatch would cause connection refused only for the affected service, while the firewall rule only permits port 6379.
C
The VPC connector is out of memory.
Why wrong: If the connector were out of memory, both services would be affected, but user-service still works.
D
The Redis instance has reached its maximum number of connections.
Why wrong: This would cause 'connection refused' for both services if the limit is reached, but user-service still works.

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 order-service code now attempts to connect to Redis on port 6380.

The order-service successfully connects to the same Redis instance before the code update. After the update, it fails with 'connection refused', while the user-service still works. Since both services share the same networking configuration and the firewall only allows port 6379, the most likely cause is that the order-service code now attempts to connect on a different port (e.g., 6380) that is not allowed by the firewall. Other options would affect both services or are inconsistent with the symptoms.

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.

✗
The order-service is deployed in a different region than the Redis instance.
Why it's wrong here
The order-service uses the same VPC connector as user-service and was working before; region mismatch would have caused issues from the start.
✓
The order-service code now attempts to connect to Redis on port 6380.
Why this is correct
A port mismatch would cause connection refused only for the affected service, while the firewall rule only permits port 6379.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
✗
The VPC connector is out of memory.
Why it's wrong here
If the connector were out of memory, both services would be affected, but user-service still works.
✗
The Redis instance has reached its maximum number of connections.
Why it's wrong here
This would cause 'connection refused' for both services if the limit is reached, but user-service still works.

Common exam traps

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

A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.

What to study next

Got this wrong? Here's your next step.

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.

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FAQ

Questions learners often ask

What does this PCA question test?

Manage implementation of cloud architecture — This question tests Manage implementation of cloud architecture — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: The order-service code now attempts to connect to Redis on port 6380. — The order-service successfully connects to the same Redis instance before the code update. After the update, it fails with 'connection refused', while the user-service still works. Since both services share the same networking configuration and the firewall only allows port 6379, the most likely cause is that the order-service code now attempts to connect on a different port (e.g., 6380) that is not allowed by the firewall. Other options would affect both services or are inconsistent with the symptoms.

What should I do if I get this PCA question wrong?

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?

CIDR notation defines the prefix length.

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