Cloud Spanner is the correct choice because it is the only Google Cloud database service that delivers strongly consistent reads across globally distributed regions with latency under 10 milliseconds while supporting high write throughput. This is achieved through TrueTime, Google’s global clock service, which enables synchronous replication and ACID transactions across continents without sacrificing performance. On the Google Professional Cloud Database Engineer exam, this scenario tests your understanding of when to choose Spanner over alternatives like Bigtable or Firestore—a common trap is assuming Bigtable’s low latency works for strong consistency, but Bigtable offers only eventual consistency. The key exam insight is that any requirement for global, strongly consistent reads under 10 ms points directly to Spanner. Memory tip: think “Spanner spans the globe with strong consistency,” linking its name to its global span and the “S” in Spanner to “strong” consistency.
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.
You are building a globally distributed leaderboard application that requires strongly consistent reads with latency under 10 ms and high write throughput. Which Google Cloud database service is most suitable?
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 strongly consistent reads across globally distributed regions with latency under 10 ms, while also supporting high write throughput. It uses TrueTime and synchronous replication to ensure ACID transactions and global consistency, meeting the exact requirements of a globally distributed leaderboard application.
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 offers eventual consistency across regions, not strong consistency.
✓
Cloud Spanner
Why this is correct
Spanner offers strong consistency across regions, low latency, and high write throughput.
Related concept
Read the scenario before looking for a memorised answer.
✗
Memorystore
Why it's wrong here
Memorystore is in-memory but not designed for globally distributed strongly consistent reads.
✗
Firestore
Why it's wrong here
Firestore has limited scaling for high write throughput and does not guarantee sub-10ms latency globally.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'low latency' with 'strong consistency' and choose Cloud Bigtable or Memorystore for their speed, overlooking the critical requirement for globally consistent reads that only Spanner can provide.
Detailed technical explanation
How to think about this question
Cloud Spanner uses TrueTime, a globally synchronized clock provided by Google's infrastructure, to enforce external consistency and linearizability across regions. It employs a two-phase commit protocol with Paxos-based replication to ensure that all writes are committed in the same order globally, which is critical for leaderboard applications where ranking updates must be immediately visible to all users. In practice, a leaderboard with millions of concurrent players updating scores would require Spanner's ability to handle thousands of writes per second per node while maintaining sub-10 ms read latency through automatic sharding and distributed query processing.
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
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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 the correct choice because it provides strongly consistent reads across globally distributed regions with latency under 10 ms, while also supporting high write throughput. It uses TrueTime and synchronous replication to ensure ACID transactions and global consistency, meeting the exact requirements of a globally distributed leaderboard application.
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.
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 →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. You are designing a database architecture for a global e-commerce application. The application requires low-latency reads in multiple regions and must handle up to 100,000 writes per second globally. Which Google Cloud database solution should you use?
medium
A.Firestore in multi-region mode.
B.Bigtable with multiple clusters.
C.Cloud SQL with cross-region replication.
✓ D.Cloud Spanner with multi-region configuration.
Why D: Cloud Spanner with a multi-region configuration is the correct choice because it provides globally distributed, strongly consistent relational database service with horizontal scalability, supporting over 100,000 writes per second across multiple regions while maintaining ACID transactions and low-latency reads via regional replicas. This meets the requirements of a global e-commerce application needing high write throughput and low read latency in multiple regions.
Variation 2. Your company is deploying a new application on Google Cloud and needs to choose a database solution. The application requires strong transactional consistency, complex SQL queries, and the ability to scale horizontally for read-heavy workloads. Which database service should you recommend?
medium
✓ A.Cloud Spanner
B.BigQuery
C.Cloud SQL
D.Cloud Firestore
Why A: Cloud Spanner is the correct choice because it provides strong transactional consistency (ACID) across globally distributed nodes, supports complex SQL queries with standard SQL syntax, and offers horizontal scaling for read-heavy workloads through automatic sharding and read replicas. Unlike other options, Spanner uniquely combines these three requirements—strong consistency, SQL, and horizontal scaling—in a single managed service.
Variation 3. A company is designing a Cloud Spanner database for a global financial application. They need to minimize latency for customer queries while handling write-heavy workloads. The current design uses a single-region instance in us-central1. Which approach should they take to reduce latency for users in Europe?
medium
A.Reconfigure the instance to a multi-region configuration with default leader in us-central1.
✓ B.Reconfigure the instance to a multi-region configuration with default leader in europe-west1.
C.Add a read-only regional replica in europe-west1.
D.Increase the number of nodes to improve throughput and automatically reduce latency.
Why B: Option D is correct because using a multi-region instance with leader options can place a read-write leader in a European region, reducing write latency for European users. Option A is wrong because read replicas in Spanner only serve stale reads (not strong reads). Option B is wrong because multi-region instance with default leader in US would not help. Option C is wrong because adding more nodes does not reduce cross-continental latency.
Variation 4. A company is designing a global application using Cloud Spanner. They need to ensure low latency reads and writes across three continents. Which TWO configurations should they consider?
hard
✓ A.Use a multi-region configuration with leader regions in each continent.
B.Use a single-region instance and rely on application caching.
C.Use strongly consistent reads from a single region.
✓ D.Use read replicas in each continent for stale read use cases.
E.Use interleaved tables to optimize query performance.
Why A: Option A is correct because Cloud Spanner multi-region configurations allow you to place leader regions in multiple continents, which enables low-latency strongly consistent reads and writes by directing traffic to the nearest leader. This is achieved through Spanner's TrueTime and Paxos-based replication, ensuring global consistency without sacrificing performance.
Last reviewed: Jun 25, 2026
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