Google PCA Design and plan a cloud solution architecture Practice Question
This PCA practice question tests your understanding of design and plan a cloud solution architecture. 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 multinational e-commerce company needs a globally distributed database that provides strong consistency and transactional support for order processing. Which Google Cloud database service should they use?
Why wrong: Cloud SQL is a regional database service and cannot be globally distributed.
B
Cloud Spanner
Cloud Spanner provides global distribution, strong consistency, and full transactional support, making it ideal for order processing.
C
Cloud Bigtable
Why wrong: Cloud Bigtable is a NoSQL wide-column database with eventual consistency, not suitable for strong transactional consistency.
D
Cloud Firestore
Why wrong: Cloud Firestore is a NoSQL document database with limited transactional support and not designed for global distribution with strong consistency.
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 is a globally distributed, horizontally scalable relational database service that provides strong consistency and full ACID transactional support across regions. Unlike other Google Cloud databases, Spanner uses synchronous replication and the TrueTime API to guarantee external consistency, making it ideal for order processing systems that require both global scale and transactional integrity.
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 SQL
Why it's wrong here
Cloud SQL is a regional database service and cannot be globally distributed.
✓
Cloud Spanner
Why this is correct
Cloud Spanner provides global distribution, strong consistency, and full transactional support, making it ideal for order processing.
Related concept
Read the scenario before looking for a memorised answer.
✗
Cloud Bigtable
Why it's wrong here
Cloud Bigtable is a NoSQL wide-column database with eventual consistency, not suitable for strong transactional consistency.
✗
Cloud Firestore
Why it's wrong here
Cloud Firestore is a NoSQL document database with limited transactional support and not designed for global distribution with strong consistency.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Cloud Spanner with Cloud SQL, assuming that a traditional relational database like Cloud SQL can be scaled globally by adding replicas, but they miss that Cloud SQL replicas are read-only and cannot provide the strong consistency and write scalability needed for a globally distributed transactional system.
Detailed technical explanation
How to think about this question
Under the hood, Cloud Spanner uses a combination of Paxos-based synchronous replication across zones and the TrueTime API (which uses GPS and atomic clocks) to assign globally unique commit timestamps, ensuring linearizability and external consistency even across continents. This means that if a customer places an order in one region and a warehouse checks inventory in another, the system guarantees that the inventory check sees the order's effect, preventing overselling. A real-world scenario where this matters is during a flash sale, where millions of users globally attempt to purchase limited stock; Spanner ensures that each transaction sees a consistent snapshot of inventory without requiring application-level conflict resolution.
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.
Design and plan a cloud solution architecture — This question tests Design and plan a cloud solution architecture — 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 is a globally distributed, horizontally scalable relational database service that provides strong consistency and full ACID transactional support across regions. Unlike other Google Cloud databases, Spanner uses synchronous replication and the TrueTime API to guarantee external consistency, making it ideal for order processing systems that require both global scale and transactional integrity.
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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