The answer is to set a retention policy and lock the bucket. This configuration enforces immutable storage compliance by preventing any object from being deleted or overwritten until the specified 7-year retention period expires, and locking the policy ensures that the rule itself cannot be removed, shortened, or disabled. On the Google Professional Cloud Developer exam, this scenario tests your understanding of how Cloud Storage’s retention policies differ from object holds—a common trap is confusing a simple retention policy (which can be removed) with a locked one, which is permanent. The key distinction is that locking is irreversible, making it the only way to meet strict regulatory requirements for immutable storage. A helpful memory tip: think of “lock and leave”—once you lock the retention policy, you leave the data untouched for the full duration, just as the regulation demands.
PCD Practice Question: Designing highly scalable, available, and reliable cloud-native applications
This PCD practice question tests your understanding of designing highly scalable, available, and reliable cloud-native applications. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 Cloud Storage for backups. They need to comply with a regulation requiring immutable storage for 7 years. Which bucket configuration should they use?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set a retention policy and lock the bucket
Option D is correct because locking a retention policy in Cloud Storage enforces immutable storage for the specified duration (7 years). Once locked, the retention policy cannot be removed or shortened, ensuring compliance with regulations that require data to be preserved in its original state and not modifiable or deletable until the retention period expires.
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 a bucket with a retention policy (not locked)
Why it's wrong here
A retention policy sets a minimum retention period, but it can be removed or shortened unless locked.
✗
Set a lifecycle rule to archive to Coldline
Why it's wrong here
Lifecycle rules change storage class but do not enforce immutability.
✗
Enable Object Versioning
Why it's wrong here
Object versioning preserves previous versions but does not prevent deletion of objects.
✓
Set a retention policy and lock the bucket
Why this is correct
Locking the retention policy makes it permanent, ensuring objects cannot be deleted or overwritten for the specified duration.
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 confuse a simple retention policy (which can be removed) with a locked retention policy (which is immutable), or they assume Object Versioning alone provides sufficient protection against deletion.
Detailed technical explanation
How to think about this question
When a retention policy is locked, Cloud Storage enforces a bucket-level minimum retention period for all objects; objects cannot be deleted or overwritten until they have been stored for the policy's duration. The lock is irreversible, and even the project owner cannot remove it, making it suitable for SEC Rule 17a-4 or similar compliance mandates. Under the hood, the retention policy is implemented via a bucket metadata field that is checked on every delete or overwrite request, and the lock is a one-way operation that sets a 'lockedTime' timestamp.
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 highly scalable, available, and reliable cloud-native applications — This question tests Designing highly scalable, available, and reliable cloud-native applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Set a retention policy and lock the bucket — Option D is correct because locking a retention policy in Cloud Storage enforces immutable storage for the specified duration (7 years). Once locked, the retention policy cannot be removed or shortened, ensuring compliance with regulations that require data to be preserved in its original state and not modifiable or deletable until the retention period expires.
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.
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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