The answer is Cloud Spanner and Firestore. Cloud Spanner is a fully managed, globally distributed relational database that uses synchronous replication and Google’s TrueTime API to deliver strong consistency and low-latency reads and writes across regions, while Firestore is a NoSQL document database that automatically replicates data across multiple regions for fast, globally consistent access. On the Google Professional Cloud Database Engineer exam, this question tests your understanding of which services handle global distribution natively versus those that require manual configuration, such as Cloud SQL or Bigtable. A common trap is confusing Cloud Bigtable, which is globally distributed but optimized for analytical throughput rather than low-latency transactional reads and writes. Memory tip: think “Spanner for SQL consistency at global scale, Firestore for serverless NoSQL with automatic multi-region replication.”
PCDE Plan and manage database infrastructure Practice Question
This PCDE practice question tests your understanding of plan and manage database infrastructure. 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.
Which TWO database services are fully managed and support global distribution of data for low-latency reads and writes?
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 a fully managed, globally distributed relational database service that provides strong consistency and horizontal scaling across regions. It supports global distribution of data for low-latency reads and writes by using synchronous replication and atomic clocks for TrueTime, enabling ACID transactions at global scale.
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.
✗
Memorystore
Why it's wrong here
Memorystore is an in-memory cache, not a database, and does not support global distribution.
✓
Cloud Spanner
Why this is correct
Cloud Spanner provides global distribution with automatic synchronous replication across regions.
Related concept
Read the scenario before looking for a memorised answer.
✓
Firestore
Why this is correct
Firestore in multi-region mode provides strong consistency and global distribution.
Related concept
Read the scenario before looking for a memorised answer.
✗
Bigtable
Why it's wrong here
Bigtable is globally distributed but is a NoSQL wide-column database, not relational.
✗
Cloud SQL
Why it's wrong here
Cloud SQL is regional; cross-region replicas are asynchronous and not fully managed global distribution.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between 'global distribution for reads and writes' versus 'global distribution for reads only'—candidates mistakenly choose Bigtable or Cloud SQL because they offer read replicas globally, but they do not support globally distributed writes with strong consistency.
Detailed technical explanation
How to think about this question
Cloud Spanner uses a combination of Paxos-based synchronous replication and TrueTime (Google's globally synchronized clock) to ensure external consistency across regions. This allows Spanner to handle globally distributed transactions with serializable isolation, a capability not available in other managed database services. In contrast, Firestore uses multi-region replication with eventual consistency for queries and strong consistency for single-document reads/writes, but it does not support complex relational joins or ACID transactions across multiple documents globally.
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.
Plan and manage database infrastructure — This question tests Plan and manage database infrastructure — 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 a fully managed, globally distributed relational database service that provides strong consistency and horizontal scaling across regions. It supports global distribution of data for low-latency reads and writes by using synchronous replication and atomic clocks for TrueTime, enabling ACID transactions at global scale.
What should I do if I get this PCDE 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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