- A
Use preemptible VMs in a managed instance group with autoscaling, and store session state in Redis (Memorystore).
Using preemptible VMs reduces cost, and storing session state in Memorystore ensures data persistence across preemptions.
- B
Change the machine type to N2 standard and use committed use discounts.
Why wrong: Switching to N2 may not reduce costs significantly and committed use discounts require a commitment.
- C
Keep local SSDs but use sole-tenant nodes to reduce contention.
Why wrong: Sole-tenant nodes increase costs, not reduce.
- D
Migrate the session state to Cloud Firestore and use preemptible VMs.
Why wrong: Correct approach but the question asks for reducing costs; this is a valid option but not the best answer because the stem says 'without sacrificing performance' and the session state is already on local SSD; moving to Firestore may add latency. Actually, the correct answer should be to use preemptible VMs, but we need to ensure the session state is externalized. Option A is partially correct but not the best because it suggests migrating session state, which might be unnecessary if using a managed instance group with autoscaling? Wait, the stem says 'store session state in files on local SSD' which is problematic for preemptible VMs because data is lost. So Option A is actually a good solution. Let me reconsider.
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. 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 runs a web application on Compute Engine instances. The application stores session state in files on local SSD. The company wants to reduce costs without sacrificing performance for a predictable traffic pattern. What should they do?
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
Use preemptible VMs in a managed instance group with autoscaling, and store session state in Redis (Memorystore).
Option A is correct because preemptible VMs reduce compute costs by up to 80%, and using a managed instance group with autoscaling handles the predictable traffic pattern efficiently. Storing session state in Redis (Memorystore) instead of local SSD ensures session data persists across VM preemptions and is shared among instances, which is critical for stateful applications. This combination maintains performance while eliminating the cost of always-on VMs.
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 preemptible VMs in a managed instance group with autoscaling, and store session state in Redis (Memorystore).
Why this is correct
Using preemptible VMs reduces cost, and storing session state in Memorystore ensures data persistence across preemptions.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Change the machine type to N2 standard and use committed use discounts.
Why it's wrong here
Switching to N2 may not reduce costs significantly and committed use discounts require a commitment.
- ✗
Keep local SSDs but use sole-tenant nodes to reduce contention.
Why it's wrong here
Sole-tenant nodes increase costs, not reduce.
- ✗
Migrate the session state to Cloud Firestore and use preemptible VMs.
Why it's wrong here
Correct approach but the question asks for reducing costs; this is a valid option but not the best answer because the stem says 'without sacrificing performance' and the session state is already on local SSD; moving to Firestore may add latency. Actually, the correct answer should be to use preemptible VMs, but we need to ensure the session state is externalized. Option A is partially correct but not the best because it suggests migrating session state, which might be unnecessary if using a managed instance group with autoscaling? Wait, the stem says 'store session state in files on local SSD' which is problematic for preemptible VMs because data is lost. So Option A is actually a good solution. Let me reconsider.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that local SSD is acceptable for session state if VMs are persistent, but the trap here is that any VM termination (preemption, maintenance, or autoscaling down) destroys local SSD data, so a shared external session store like Redis is mandatory when using preemptible or autoscaled instances.
Detailed technical explanation
How to think about this question
Memorystore for Redis provides sub-millisecond latency for session reads/writes using the Redis protocol (TCP port 6379), and it supports replication and persistence (AOF/RDB) for high availability. Preemptible VMs in a managed instance group use the Google Compute Engine preemption lifecycle (30-second notice) and autoscaling metrics (e.g., CPU utilization) to match the predictable traffic pattern, while the Redis instance acts as a centralized session store decoupled from ephemeral compute. In a real-world scenario, this pattern is common for e-commerce flash sales where traffic spikes are predictable and cost optimization is critical.
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
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FAQ
Questions learners often ask
What does this PCA question test?
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: Use preemptible VMs in a managed instance group with autoscaling, and store session state in Redis (Memorystore). — Option A is correct because preemptible VMs reduce compute costs by up to 80%, and using a managed instance group with autoscaling handles the predictable traffic pattern efficiently. Storing session state in Redis (Memorystore) instead of local SSD ensures session data persists across VM preemptions and is shared among instances, which is critical for stateful applications. This combination maintains performance while eliminating the cost of always-on VMs.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 30, 2026
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