- A
Use Cloud Spanner to auto-scale.
Why wrong: Migration to Spanner is complex and unnecessary for a short peak.
- B
Upgrade to a higher-tier machine type permanently.
Why wrong: Permanent upgrade costs more and is wasteful for a short peak.
- C
Add read replicas and rewrite queries to use replicas for reads.
Why wrong: Read replicas do not help with write throughput.
- D
Increase vCPU and memory to 32 vCPU/128 GB temporarily for the peak window.
Vertical scaling is straightforward and temporary, minimizing cost.
Question 438 of 1,000
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.
An online retailer uses Cloud SQL for PostgreSQL. They need to scale for a seasonal peak. They expect 2x current traffic. Their current instance is 16 vCPU, 64 GB RAM, 1 TB storage. The peak lasts 4 hours. They want to handle it without downtime. What is the best approach?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
✓
Increase vCPU and memory to 32 vCPU/128 GB temporarily for the peak window.
Option D is correct because Cloud SQL for PostgreSQL supports vertical scaling with minimal downtime, and temporarily increasing vCPU and memory to 32 vCPU/128 GB for the 4-hour peak window meets the 2x traffic demand without requiring application changes. This approach avoids permanent cost increases and leverages Cloud SQL's ability to scale up and down via the gcloud command or console, with only a brief failover (typically under 60 seconds) that can be scheduled during a maintenance window to achieve near-zero downtime.
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 Cloud Spanner to auto-scale.
Why it's wrong here
Migration to Spanner is complex and unnecessary for a short peak.
- ✗
Upgrade to a higher-tier machine type permanently.
Why it's wrong here
Permanent upgrade costs more and is wasteful for a short peak.
- ✗
Add read replicas and rewrite queries to use replicas for reads.
Why it's wrong here
Read replicas do not help with write throughput.
- ✓
Increase vCPU and memory to 32 vCPU/128 GB temporarily for the peak window.
Why this is correct
Vertical scaling is straightforward and temporary, minimizing cost.
Clue confirmation
The clue word "best" 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
The Google Cloud Professional Database Engineer exam often tests the misconception that read replicas can handle all traffic scaling (including writes), but the trap here is that read replicas do not increase write capacity, so for a 2x traffic mix that includes writes, vertical scaling of the primary instance is the only viable single-database solution without downtime.
Detailed technical explanation
How to think about this question
Cloud SQL for PostgreSQL uses a primary-instance architecture where vertical scaling (changing machine type) triggers a restart or failover, but with a maintenance window or using the `--no-restart` flag, the instance can be scaled with minimal disruption. Under the hood, Cloud SQL leverages Compute Engine live migration for some changes, but vCPU/memory upgrades require a new VM, so the downtime is typically a few seconds to a minute. In real-world scenarios, this approach is ideal for predictable seasonal peaks, as it avoids the latency and consistency trade-offs of read replicas or the complexity of sharding with Spanner.
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.
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FAQ
Questions learners often ask
What does this PCDE question test?
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: Increase vCPU and memory to 32 vCPU/128 GB temporarily for the peak window. — Option D is correct because Cloud SQL for PostgreSQL supports vertical scaling with minimal downtime, and temporarily increasing vCPU and memory to 32 vCPU/128 GB for the 4-hour peak window meets the 2x traffic demand without requiring application changes. This approach avoids permanent cost increases and leverages Cloud SQL's ability to scale up and down via the gcloud command or console, with only a brief failover (typically under 60 seconds) that can be scheduled during a maintenance window to achieve near-zero downtime.
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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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