PCDOE Optimizing service performance Practice Question
This PCDOE practice question tests your understanding of optimizing service performance. 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.
Exhibit
NAME ZONE MACHINE_TYPE PREEMPTIBLE
instance-1 us-central1-a n1-standard-2 yes
instance-2 us-central1-a n1-highcpu-16 no
instance-3 us-central1-b n1-highmem-8 no
Refer to the exhibit. A team runs a batch processing job on these instances. The job is CPU-bound and can tolerate interruptions. Which instance is the most cost-effective for this workload?
NAME ZONE MACHINE_TYPE PREEMPTIBLE
instance-1 us-central1-a n1-standard-2 yes
instance-2 us-central1-a n1-highcpu-16 no
instance-3 us-central1-b n1-highmem-8 no
A
instance-3
Why wrong: instance-3 is not preemptible and memory-optimized, not ideal for CPU-bound tasks.
B
None, they should use a different machine type
Why wrong: instance-1 is appropriate.
C
instance-1
Correct. Preemptible instance with sufficient CPU at low cost.
D
instance-2
Why wrong: instance-2 is not preemptible, higher cost.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
instance-1
Instance-1 is the most cost-effective because it is a preemptible (or spot) VM, which is significantly cheaper than standard on-demand instances. Since the batch processing job is CPU-bound and can tolerate interruptions, preemptible instances are ideal for this workload, offering up to 60-91% cost savings while still providing the necessary compute capacity.
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.
✗
instance-3
Why it's wrong here
instance-3 is not preemptible and memory-optimized, not ideal for CPU-bound tasks.
✗
None, they should use a different machine type
Why it's wrong here
instance-1 is appropriate.
✓
instance-1
Why this is correct
Correct. Preemptible instance with sufficient CPU at low cost.
Related concept
Read the scenario before looking for a memorised answer.
✗
instance-2
Why it's wrong here
instance-2 is not preemptible, higher cost.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that any preemptible instance is automatically the best choice, but the trap here is that candidates might overlook whether the workload can actually tolerate interruptions or whether the specific instance type (e.g., with GPUs or high memory) is over-provisioned for a CPU-bound job.
Detailed technical explanation
How to think about this question
Preemptible instances in Google Cloud are Compute Engine VMs that last up to 24 hours and can be terminated at any time if resources are needed elsewhere, but they cost about 60-80% less than standard instances. For CPU-bound batch jobs, using preemptible instances with a managed instance group and a queued job system (like Cloud Batch or a custom retry logic) ensures cost efficiency while handling interruptions gracefully. This approach is common in data processing pipelines (e.g., using Apache Beam or Spark) where checkpointing allows resumption from the last saved state.
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 — 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: instance-1 — Instance-1 is the most cost-effective because it is a preemptible (or spot) VM, which is significantly cheaper than standard on-demand instances. Since the batch processing job is CPU-bound and can tolerate interruptions, preemptible instances are ideal for this workload, offering up to 60-91% cost savings while still providing the necessary compute capacity.
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.
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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