The correct answer is to refactor the application to write state to a persistent service like Cloud Storage. This is because local SSD on a preemptible VM is ephemeral and is destroyed upon preemption or termination, making it unsuitable for critical data. By designing the workload to be stateless and storing state externally, you decouple data durability from the VM lifecycle, which is the core principle behind preemptible VM state persistence with Cloud Storage. On the Google Professional Cloud Developer exam, this scenario tests your understanding of architecting for fault tolerance and cost optimization, where the common trap is assuming local SSD persists across instance restarts. A helpful memory tip is "SSD is Scratch, Storage is Stored"—local SSD is for temporary scratch data, while Cloud Storage provides durable, persistent storage for your application state.
PCD Building and testing applications Practice Question
This PCD practice question tests your understanding of building and testing applications. 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 deploys a Java application on Compute Engine with a preemptible VM instance group managed by an instance template. The application writes critical state to local SSD. After a preemption event, the new instance starts fresh and loses state. What is the best practice to ensure state persistence?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Refactor the application to write state to a persistent service like Cloud Storage
Option B is correct because local SSD data is ephemeral and lost on VM preemption or termination. Refactoring the application to write critical state to a persistent service like Cloud Storage ensures data durability independent of the VM lifecycle. This aligns with the best practice of designing preemptible workloads to be stateless, where state is stored externally.
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.
✗
Modify the startup script to recover state from a snapshot
Why it's wrong here
Snapshots are for persistent disks, not local SSDs; also recovery from snapshot is not real-time.
✓
Refactor the application to write state to a persistent service like Cloud Storage
Why this is correct
This decouples state from the instance, ensuring durability across preemptions.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure the managed instance group as stateful to preserve local SSD data
Why it's wrong here
Stateful MIGs preserve instance name and disks but local SSDs are still ephemeral.
✗
Use a regular (non-preemptible) VM instead of preemptible
Why it's wrong here
This avoids preemption but increases cost; the question asks for best practice with preemptible VMs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that local SSD can be made persistent through MIG stateful configuration, but stateful MIGs do not protect against preemption—they only preserve instance name and metadata, not local SSD data on termination.
Detailed technical explanation
How to think about this question
Preemptible VMs in Compute Engine have a maximum lifetime of 24 hours and can be terminated at any time, making local SSD unsuitable for persistent state. Cloud Storage provides a highly available, durable object store with strong consistency for write-once-read-many patterns; for transactional state, consider Cloud Spanner or Firestore. The instance template's startup script can then read state from Cloud Storage on boot, enabling stateless, resilient application design.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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.
Building and testing applications — This question tests Building and testing applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Refactor the application to write state to a persistent service like Cloud Storage — Option B is correct because local SSD data is ephemeral and lost on VM preemption or termination. Refactoring the application to write critical state to a persistent service like Cloud Storage ensures data durability independent of the VM lifecycle. This aligns with the best practice of designing preemptible workloads to be stateless, where state is stored externally.
What should I do if I get this PCD 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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Question Discussion
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