- A
Cloud Spanner
Spanner provides global ACID transactions, 99.999% SLA, and automatic failover across regions.
- B
AlloyDB with cross-region replicas
Why wrong: AlloyDB is PostgreSQL-compatible but cross-region replicas are asynchronous, not strong ACID across regions.
- C
Cloud SQL with cross-region replicas
Why wrong: Cloud SQL does not provide strong ACID across regions; replication is asynchronous and may have lag.
- D
Firestore in Native mode
Why wrong: Firestore does not support ACID transactions across regions; its multi-region mode has eventual consistency.
Question 237 of 980
Design Scalable and Highly Available Cloud Database Solutions →mediumMultiple ChoiceObjective-mapped
PCD Practice Question: Design Scalable and Highly Available Cloud Database Solutions
This PCD practice question tests your understanding of design scalable and highly available cloud database solutions. 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 financial services company is building a global payment system that requires strong ACID transactions across multiple regions, with 99.999% availability and automatic failover. Which Google Cloud database should they choose?
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
✓
Cloud Spanner
Cloud Spanner is the only Google Cloud database that provides strong ACID transactions across multiple regions with 99.999% availability and automatic failover. It uses a globally distributed architecture with synchronous replication and the TrueTime API to ensure external consistency, making it ideal for a global payment system that requires strict consistency and high 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.
- ✓
Cloud Spanner
Why this is correct
Spanner provides global ACID transactions, 99.999% SLA, and automatic failover across regions.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
AlloyDB with cross-region replicas
Why it's wrong here
AlloyDB is PostgreSQL-compatible but cross-region replicas are asynchronous, not strong ACID across regions.
- ✗
Cloud SQL with cross-region replicas
Why it's wrong here
Cloud SQL does not provide strong ACID across regions; replication is asynchronous and may have lag.
- ✗
Firestore in Native mode
Why it's wrong here
Firestore does not support ACID transactions across regions; its multi-region mode has eventual consistency.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that cross-region replicas in relational databases like AlloyDB or Cloud SQL can provide strong ACID transactions and 99.999% availability, but these solutions use asynchronous replication and lack the global consistency and automatic failover capabilities of Cloud Spanner.
Detailed technical explanation
How to think about this question
Cloud Spanner achieves 99.999% availability through a combination of synchronous Paxos-based replication across zones and regions, and automatic failover handled by the underlying Google infrastructure. The TrueTime API provides globally consistent timestamps, enabling external consistency for distributed transactions without the performance penalty of traditional two-phase commit across wide-area networks. In a real-world scenario, a global payment system using Spanner can execute a cross-region transfer with read-write transactions that are serializable, ensuring no double-spending or lost updates even during regional outages.
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.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this PCD question test?
Design Scalable and Highly Available Cloud Database Solutions — This question tests Design Scalable and Highly Available Cloud Database Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Cloud Spanner — Cloud Spanner is the only Google Cloud database that provides strong ACID transactions across multiple regions with 99.999% availability and automatic failover. It uses a globally distributed architecture with synchronous replication and the TrueTime API to ensure external consistency, making it ideal for a global payment system that requires strict consistency and high availability.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jul 4, 2026
This PCD practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCD exam.
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