- A
Cloud Bigtable
Why wrong: Bigtable provides strong consistency but does not support ACID transactions across rows.
- B
Cloud SQL
Why wrong: Cloud SQL does not provide global distribution.
- C
Firestore
Why wrong: Firestore has strict throughput limits and is not designed for millions of writes per second.
- D
Cloud Spanner
Spanner offers global strong consistency, ACID transactions, and horizontal scaling.
Question 133 of 1,000
PCDOE Design and Plan Database Solutions Practice Question
This PCDOE practice question tests your understanding of design and plan 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.
An engineer is designing a global inventory system that requires strong consistency across continents, with the ability to handle write conflicts and ensure ACID transactions. The system expects millions of reads and writes per second. Which Google Cloud database service meets these requirements?
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 correct choice because it provides ACID transactions and strong consistency across globally distributed regions, using TrueTime and synchronous replication to handle write conflicts at scale. It is designed for millions of reads and writes per second while maintaining external consistency, making it ideal for a global inventory system.
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 Bigtable
Why it's wrong here
Bigtable provides strong consistency but does not support ACID transactions across rows.
- ✗
Cloud SQL
Why it's wrong here
Cloud SQL does not provide global distribution.
- ✗
Firestore
Why it's wrong here
Firestore has strict throughput limits and is not designed for millions of writes per second.
- ✓
Cloud Spanner
Why this is correct
Spanner offers global strong consistency, ACID transactions, and horizontal scaling.
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 often confuse Firestore's strong consistency within a single region with global consistency, overlooking the need for ACID transactions and conflict resolution at planetary scale, which only Cloud Spanner provides.
Detailed technical explanation
How to think about this question
Cloud Spanner uses TrueTime, a globally synchronized clock based on GPS and atomic clocks, to assign commit timestamps that ensure external consistency across continents. Under the hood, it employs Paxos-based synchronous replication and two-phase commit to resolve write conflicts, guaranteeing ACID properties even with millions of concurrent transactions. In a real-world scenario, a global inventory system must avoid overselling stock due to latency, and Spanner's strong consistency prevents such anomalies by serializing writes across regions.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this PCDOE question test?
Design and Plan Database Solutions — This question tests Design and Plan 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 correct choice because it provides ACID transactions and strong consistency across globally distributed regions, using TrueTime and synchronous replication to handle write conflicts at scale. It is designed for millions of reads and writes per second while maintaining external consistency, making it ideal for a global inventory system.
What should I do if I get this PCDOE 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
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Last reviewed: Jul 4, 2026
This PCDOE 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 PCDOE exam.
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