PDE Designing data processing systems Practice Question
This PDE practice question tests your understanding of designing data processing systems. 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 uses Dataproc for transient clusters. Which TWO actions can reduce costs?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set cluster autoscaling to minimize idle resources
Option B is correct because Dataproc cluster autoscaling automatically adjusts the number of worker nodes based on the YARN memory and CPU utilization metrics. By scaling down during idle periods, you avoid paying for unused compute capacity, directly reducing costs for transient clusters that have variable workloads.
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.
✗
Increase master node size
Why it's wrong here
Larger master node increases cost.
✓
Set cluster autoscaling to minimize idle resources
Read the scenario before looking for a memorised answer.
✗
Use standard VMs for all nodes
Why it's wrong here
Standard VMs are more expensive than preemptible.
✗
Use persistent clusters to avoid creation overhead
Why it's wrong here
Persistent clusters cost when idle.
✓
Use preemptible VMs for worker nodes
Why this is correct
Preemptible VMs are cheaper and suitable for transient workloads.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think 'persistent clusters' are cheaper because they avoid re-creation overhead, but they overlook the continuous compute cost of idle persistent clusters versus the pay-per-use model of transient clusters.
Detailed technical explanation
How to think about this question
Dataproc autoscaling uses the YARN ResourceManager metrics (e.g., pending containers, memory available) to trigger scale-up or scale-down actions via the Compute Engine instance group manager. The cooldown period (default 120 seconds) prevents flapping, and you can set a minimum number of instances to avoid scaling to zero. Preemptible VMs can be up to 80% cheaper than standard VMs, but they are terminated by Compute Engine within 24 hours; for transient clusters with checkpointed jobs, this is acceptable and significantly reduces cost.
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.
Designing data processing systems — This question tests Designing data processing systems — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Set cluster autoscaling to minimize idle resources — Option B is correct because Dataproc cluster autoscaling automatically adjusts the number of worker nodes based on the YARN memory and CPU utilization metrics. By scaling down during idle periods, you avoid paying for unused compute capacity, directly reducing costs for transient clusters that have variable workloads.
What should I do if I get this PDE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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