The answer is that the Cloud Spanner instance lacks a read replica in the region close to the clients. This is correct because Cloud Spanner’s multi-region configurations rely on regional replicas to serve reads locally; without a replica in the requesting region, even stale reads must traverse the network to the nearest available replica, and physical distance directly increases latency regardless of data distribution. On the Google Professional Cloud Architect exam, this scenario tests your understanding of Cloud Spanner’s replication architecture and the distinction between compute and storage locality—a common trap is assuming stale reads bypass network distance. Remember the memory tip: “No local replica, no low latency,” meaning that for high latency read requests in a specific region, always check the replica placement first.
Google PCA Manage implementation of cloud architecture Practice Question
This PCA practice question tests your understanding of manage implementation of cloud architecture. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 organization has deployed a multi-region Cloud Spanner instance for a global application. The application is experiencing high latency for read requests from a specific region. The team has verified that the application is using stale reads and the data distribution is even. What is the most likely cause of the high latency?
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 Spanner instance does not have a read replica in a location close to the clients.
Option D is correct because Cloud Spanner uses a single global configuration with regional read replicas. If the instance does not have a read replica in the region where the clients are located, read requests must traverse the network to a replica in another region, causing higher latency. Even with stale reads, the physical distance to the nearest replica directly impacts read latency.
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 number of read replicas in the region is insufficient to handle the read volume.
Why it's wrong here
While more replicas can help, the primary cause is likely the distance to the nearest replica.
✗
The Spanner instance has too few nodes, causing contention.
Why it's wrong here
Contention typically affects write latency, not stale reads.
✗
The application is using read-write transactions instead of read-only transactions.
Why it's wrong here
Read-write transactions involve strong reads and may increase latency, but the question states the application is using stale reads.
✓
The Spanner instance does not have a read replica in a location close to the clients.
Why this is correct
Adding a read replica in the region reduces network round-trip time, lowering read latency.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that adding more nodes or read replicas solves regional latency, when the real issue is the absence of a local replica in the specific region.
Detailed technical explanation
How to think about this question
Cloud Spanner's multi-region configurations use a single primary region for writes and multiple witness or read-only regions for reads. Stale reads can be served from any replica, but if no replica exists in the client's region, the read must be forwarded to the nearest available replica, incurring cross-region network latency. This is a common pitfall when deploying global applications without ensuring regional read capacity.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this PCA question in full detail.
Manage implementation of cloud architecture — This question tests Manage implementation of cloud architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The Spanner instance does not have a read replica in a location close to the clients. — Option D is correct because Cloud Spanner uses a single global configuration with regional read replicas. If the instance does not have a read replica in the region where the clients are located, read requests must traverse the network to a replica in another region, causing higher latency. Even with stale reads, the physical distance to the nearest replica directly impacts read latency.
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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Question Discussion
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