Google PCA Ensure solution and operations reliability Practice Question
This PCA practice question tests your understanding of ensure solution and operations reliability. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 Spanner for a global financial application. They need to ensure that a regional outage does not cause data loss. The application requires strong consistency and low latency reads and writes across multiple regions. Which configuration meets the reliability requirements?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a multi-region Spanner instance with a primary region and two witness regions
Option C is correct because a multi-region Spanner instance with a primary region and two witness regions uses Google's synchronous replication across three regions, ensuring strong consistency and no data loss during a regional outage. Witness regions participate in the Paxos quorum without serving read traffic, guaranteeing that writes are committed in at least two regions before acknowledgment, which meets the requirement for zero data loss and low latency reads and writes.
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 multi-region Spanner instance with read replicas in two other regions
Why it's wrong here
Incorrect: Spanner doesn't use read replicas; it uses synchronous replication.
✗
Use a single-region Spanner instance and schedule backups to Cloud Storage
Use a multi-region Spanner instance with a primary region and two witness regions
Why this is correct
Correct: provides synchronous replication and automatic failover.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use a single-region Spanner instance with point-in-time recovery (PITR) enabled
Why it's wrong here
Incorrect: single-region fails during regional outage.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that read replicas or backups can prevent data loss during a regional outage, but in Spanner, only synchronous replication via a multi-region instance with a quorum of regions (including witness regions) guarantees zero data loss and strong consistency across regions.
Detailed technical explanation
How to think about this question
Spanner's multi-region configuration uses the Paxos consensus protocol to replicate data across three regions, with each write requiring a quorum of at least two regions (including the leader) to commit, ensuring strong consistency and durability. Witness regions are a cost-optimized option that participate in the Paxos quorum but do not serve read traffic, reducing compute costs while maintaining the same reliability guarantees as full replicas. In a real-world scenario, if the primary region fails, Spanner automatically elects a new leader from one of the remaining regions, and no committed data is lost because the quorum ensures at least two regions have the latest writes.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this PCA question in full detail.
Ensure solution and operations reliability — This question tests Ensure solution and operations reliability — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a multi-region Spanner instance with a primary region and two witness regions — Option C is correct because a multi-region Spanner instance with a primary region and two witness regions uses Google's synchronous replication across three regions, ensuring strong consistency and no data loss during a regional outage. Witness regions participate in the Paxos quorum without serving read traffic, guaranteeing that writes are committed in at least two regions before acknowledgment, which meets the requirement for zero data loss and low latency reads and writes.
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.
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Question Discussion
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