- A
Cloud SQL
Why wrong: Cloud SQL is a relational database with a single primary; it does not scale writes horizontally.
- B
Firestore
Firestore is a NoSQL database that offers strong consistency and automatically scales horizontally, including for writes.
- C
AlloyDB
Why wrong: AlloyDB provides strong consistency but only scales reads horizontally via read pools; writes are handled by a single primary, so it does not meet the write scalability requirement.
- D
Cloud Spanner
Cloud Spanner is designed for strong consistency and horizontal scaling globally, meeting both requirements.
- E
Bigtable
Why wrong: Bigtable is eventually consistent and not suitable for strong consistency requirements.
Question 878 of 999
Design Scalable and Highly Available Cloud Database Solutions →mediumMultiple SelectObjective-mapped
PCD Strong consistency Practice Question
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. A key principle to apply: strong consistency. 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.
Your company runs a global e-commerce platform that requires strong consistency for transactions and the ability to scale writes horizontally. You are evaluating database options. Which TWO Google Cloud databases meet these requirements? (Choose 2)
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
✓
Firestore
Cloud Spanner provides strong consistency and horizontal scaling globally, making it ideal for a global e-commerce platform. Firestore is a NoSQL database that also offers strong consistency and automatic horizontal scaling for writes, meeting the requirement for write scalability. AlloyDB, while providing strong consistency, does not scale writes horizontally; it relies on a single primary for writes. Cloud SQL and Bigtable do not meet both requirements: Cloud SQL lacks horizontal write scaling, and Bigtable does not provide strong consistency.
Key principle: Strong consistency
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 SQL
Why it's wrong here
Cloud SQL is a relational database with a single primary; it does not scale writes horizontally.
- ✓
Firestore
Why this is correct
Firestore is a NoSQL database that offers strong consistency and automatically scales horizontally, including for writes.
Related concept
Strong consistency
- ✗
AlloyDB
Why it's wrong here
AlloyDB provides strong consistency but only scales reads horizontally via read pools; writes are handled by a single primary, so it does not meet the write scalability requirement.
- ✓
Cloud Spanner
Why this is correct
Cloud Spanner is designed for strong consistency and horizontal scaling globally, meeting both requirements.
Related concept
Strong consistency
- ✗
Bigtable
Why it's wrong here
Bigtable is eventually consistent and not suitable for strong consistency requirements.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Strong consistency
- Horizontal write scalability
- Cloud Spanner
- Firestore
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
Strong consistency
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.
Review strong consistency, then practise related PCD questions on the same topic to reinforce the concept.
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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 — Strong consistency.
What is the correct answer to this question?
The correct answer is: Firestore — Cloud Spanner provides strong consistency and horizontal scaling globally, making it ideal for a global e-commerce platform. Firestore is a NoSQL database that also offers strong consistency and automatic horizontal scaling for writes, meeting the requirement for write scalability. AlloyDB, while providing strong consistency, does not scale writes horizontally; it relies on a single primary for writes. Cloud SQL and Bigtable do not meet both requirements: Cloud SQL lacks horizontal write scaling, and Bigtable does not provide strong consistency.
What should I do if I get this PCD question wrong?
Review strong consistency, then practise related PCD questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Strong consistency
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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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