PCDE Plan and manage database infrastructure Practice Question
This PCDE practice question tests your understanding of plan and manage database infrastructure. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 has a Spanner instance with 5 nodes serving a global application. They receive alerts that write latency has increased significantly during business hours in the Asia-Pacific region. The team confirms that no application changes have been made. What is the most likely cause and recommended action?
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
✓
Writes are hitting a hot spot due to monotonically increasing keys; consider using a hash prefix or bit-reversed key
Monotonically increasing keys (e.g., timestamps or auto-increment IDs) cause all new writes to target the same tablet leader in Spanner, creating a hot spot. This increases write latency because the single node becomes a bottleneck, especially during peak business hours in the Asia-Pacific region. Using a hash prefix or bit-reversed key distributes writes evenly across nodes, resolving the 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.
✓
Writes are hitting a hot spot due to monotonically increasing keys; consider using a hash prefix or bit-reversed key
Why this is correct
Using a hash prefix or bit-reversed key distributes writes across splits, reducing hot spots.
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.
✗
CPU utilization is above 70%; enable Spanner fine-grained access control
Why it's wrong here
Access control does not affect write latency.
✗
Set up interleaved indexes to speed up writes
Why it's wrong here
Interleaved indexes are for read performance; they do not reduce write hot spots.
✗
The instance is under-provisioned; increase the number of nodes
Why it's wrong here
Adding nodes helps overall throughput but does not fix hot spotting; might even spread load unevenly.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that adding nodes (scaling out) always fixes write latency, but the real issue is often a hot spot from poor key design, which requires schema-level changes rather than infrastructure scaling.
Detailed technical explanation
How to think about this question
Spanner uses TrueTime and Paxos-based replication; each split (tablet) has a leader that handles writes. Monotonically increasing keys cause all writes to go to the same split, overloading that leader and its replicas. Bit-reversed keys or hash prefixes spread writes across splits, leveraging Spanner's automatic split management to balance load without manual re-sharding.
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.
Plan and manage database infrastructure — This question tests Plan and manage database infrastructure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Writes are hitting a hot spot due to monotonically increasing keys; consider using a hash prefix or bit-reversed key — Monotonically increasing keys (e.g., timestamps or auto-increment IDs) cause all new writes to target the same tablet leader in Spanner, creating a hot spot. This increases write latency because the single node becomes a bottleneck, especially during peak business hours in the Asia-Pacific region. Using a hash prefix or bit-reversed key distributes writes evenly across nodes, resolving the contention.
What should I do if I get this PCDE 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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