- A
The transaction is experiencing contention due to a hot spot
Contention on popular keys causes retries and delays.
- B
The transaction is using stale reads
Why wrong: Stale reads bypass locks and are faster.
- C
The transaction is not using a read-write transaction
Why wrong: Read-only transactions are typically faster, not slower.
- D
The transaction is too large
Why wrong: Large transactions can be slow but less common than hot spots.
Question 848 of 1,000
PCDOE Optimizing service performance Practice Question
This PCDOE practice question tests your understanding of optimizing service performance. 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.
A financial services company uses Spanner for their core database. They notice that some transactions are taking longer than expected, especially during cross-region writes. They have set up Spanner with regional configuration. 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.
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 transaction is experiencing contention due to a hot spot
A is correct because cross-region writes in a regional Spanner configuration can lead to increased latency due to hot spotting. A hot spot occurs when many writes are concentrated on a single split (e.g., a monotonically increasing key), causing contention and serialization delays. This is especially pronounced in cross-region scenarios because Spanner's TrueTime and Paxos-based replication require consensus across zones, amplifying the impact of contention.
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 transaction is experiencing contention due to a hot spot
Why this is correct
Contention on popular keys causes retries and delays.
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 transaction is using stale reads
Why it's wrong here
Stale reads bypass locks and are faster.
- ✗
The transaction is not using a read-write transaction
Why it's wrong here
Read-only transactions are typically faster, not slower.
- ✗
The transaction is too large
Why it's wrong here
Large transactions can be slow but less common than hot spots.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that cross-region latency is solely due to network distance, but the real trap is that regional configuration still suffers from hot spots because all writes must go to the leader replica, and contention on a split can cause disproportionate delays.
Detailed technical explanation
How to think about this question
Spanner uses a global clock (TrueTime) and a Paxos-based replication protocol to ensure consistency across regions. In a regional configuration, all replicas are in one region, so cross-region writes still incur network round-trips to the leader replica. A hot spot on a single split forces serialized writes, as Spanner uses pessimistic locking for read-write transactions, and the leader must coordinate with a quorum of replicas, amplifying latency under contention.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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.
- →
Optimizing service performance — study guide chapter
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FAQ
Questions learners often ask
What does this PCDOE question test?
Optimizing service performance — This question tests Optimizing service performance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The transaction is experiencing contention due to a hot spot — A is correct because cross-region writes in a regional Spanner configuration can lead to increased latency due to hot spotting. A hot spot occurs when many writes are concentrated on a single split (e.g., a monotonically increasing key), causing contention and serialization delays. This is especially pronounced in cross-region scenarios because Spanner's TrueTime and Paxos-based replication require consensus across zones, amplifying the impact of contention.
What should I do if I get this PCDOE 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.
About these practice questions
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Last reviewed: Jul 4, 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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