Google PCA Practice Question: Analyze and optimize technical and business processes
This PCA practice question tests your understanding of analyze and optimize technical and business processes. 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 Cloud Spanner instance is experiencing high latency for point reads. The instance has 5 nodes and the read throughput is moderate. The table has a primary key with monotonically increasing values. What is the most likely cause and optimization?
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.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The primary key design causes hotspotting; use a hash prefix or add a leading random value.
The monotonically increasing primary key causes all writes to be directed to the last tablet (splitting point), creating a hotspot on one node. This hotspot leads to high latency for point reads because that node becomes a bottleneck. Adding a hash prefix or a leading random value distributes writes and reads evenly across all nodes, resolving the hotspotting issue.
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.
✗
Use interleaved tables to reduce the number of index lookups.
Why it's wrong here
Interleaved tables don't address hotspotting from monotonic keys.
✗
The instance is underprovisioned; add more nodes.
Why it's wrong here
Adding nodes may help but the root cause is likely hotspotting.
✓
The primary key design causes hotspotting; use a hash prefix or add a leading random value.
Why this is correct
This distributes writes across splits.
Clue confirmation
The clue words "most likely", "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The instance has too many nodes causing transaction conflicts; reduce nodes.
Why it's wrong here
Less nodes would increase latency.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that adding more nodes solves all performance issues, but here the problem is a design flaw (hotspotting) that requires a key distribution strategy, not more capacity.
Detailed technical explanation
How to think about this question
Cloud Spanner splits tablets based on key ranges; with a monotonically increasing key, all new writes land in the last tablet, causing that node to handle a disproportionate share of reads and writes. Using a hash prefix (e.g., SHA256 of the original key) or a leading random value (e.g., a UUID prefix) ensures uniform distribution across all splits, eliminating the hotspot. This is a common pattern for time-series or sequential ID tables in distributed databases.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this PCA question in full detail.
Analyze and optimize technical and business processes — This question tests Analyze and optimize technical and business processes — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The primary key design causes hotspotting; use a hash prefix or add a leading random value. — The monotonically increasing primary key causes all writes to be directed to the last tablet (splitting point), creating a hotspot on one node. This hotspot leads to high latency for point reads because that node becomes a bottleneck. Adding a hash prefix or a leading random value distributes writes and reads evenly across all nodes, resolving the hotspotting issue.
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", "primary". 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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