Google PCA Ensure solution and operations reliability Practice Question
This PCA practice question tests your understanding of ensure solution and operations reliability. 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 global application uses Cloud Spanner with a multi-region configuration. During a regional outage, some transactions are failing. What is the recommended approach to maintain write availability?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure Spanner with leader-based replication and rely on automatic failover
Cloud Spanner's multi-region configuration uses leader-based replication, where each region has a leader for its read-write replicas. During a regional outage, Spanner automatically fails over the leader to another region, ensuring write availability without manual intervention. This is the recommended approach because it leverages Spanner's built-in synchronous replication and automatic failover to maintain consistency and availability.
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.
✗
Implement application-level retry with exponential backoff
Why it's wrong here
Retry improves resilience to transient errors but does not address regional failures.
✗
Use a single-region Spanner instance with a standby in a different zone
Why it's wrong here
A single-region instance cannot survive a full regional outage.
✓
Configure Spanner with leader-based replication and rely on automatic failover
Why this is correct
Spanner automatically fails over to another region if the leader region fails.
Related concept
Read the scenario before looking for a memorised answer.
✗
Manually failover to a different region using a script
Why it's wrong here
Manual intervention increases recovery time and risk of misconfiguration.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse Spanner's automatic failover with manual failover approaches used in traditional databases, or assume that application-level retry alone can compensate for a regional outage, ignoring Spanner's built-in leader election and synchronous replication.
Detailed technical explanation
How to think about this question
Spanner's multi-region configuration uses the Paxos protocol to elect a leader for each split (shard) across regions. When a region fails, Spanner automatically re-elects leaders in remaining regions within seconds, using synchronous replication to ensure no data loss. This is distinct from asynchronous replication models like MySQL or Cassandra, where manual failover or eventual consistency might be required.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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: Configure Spanner with leader-based replication and rely on automatic failover — Cloud Spanner's multi-region configuration uses leader-based replication, where each region has a leader for its read-write replicas. During a regional outage, Spanner automatically fails over the leader to another region, ensuring write availability without manual intervention. This is the recommended approach because it leverages Spanner's built-in synchronous replication and automatic failover to maintain consistency and availability.
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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