- A
Shard the database across multiple regional instances based on user geography.
Why wrong: Sharding across instances complicates schema and transactions, and Spanner multi-region is the recommended approach.
- B
Create read replicas in other regions to offload read traffic and keep writes in the primary region.
Why wrong: Read replicas do not help with write latency or write capacity.
- C
Change the instance configuration to a multi-region configuration like nam3 (us-central1, us-east1, us-west1) and configure a dedicated write region.
Multi-region configurations provide low-latency writes by placing processing close to users and ensure high availability.
- D
Increase the number of nodes in the existing regional instance to handle the increased write capacity.
Why wrong: This only scales within one region; write latency from other regions will still be high.
Quick Answer
The correct choice is to change the instance configuration to a multi-region configuration like nam3 (us-central1, us-east1, us-west1) and configure a dedicated write region. This works because Cloud Spanner’s multi-region configurations use synchronous replication within the write region for strong consistency and fast local writes, while asynchronously replicating to other regions for global read availability—enabling global write scaling without sacrificing low latency. On the Google Professional Cloud Database Engineer exam, this scenario tests your understanding of how to scale write capacity across geographies; a common trap is choosing a single-region upgrade or a read-only replica, which cannot handle the 10x write increase globally. Remember the key distinction: multi-region configurations are for write scaling and availability, not just read distribution. A useful memory tip is “write where you commit, read where you sit”—the dedicated write region handles all commits, so place it near your primary user base.
PCDE Plan and manage database infrastructure Practice Question
This PCDE practice question tests your understanding of plan and manage database infrastructure. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 retail company uses Cloud Spanner to handle global transaction processing. The database has a single regional instance in us-central1. The company expects a 10x increase in write traffic from a new mobile app. The database engineer needs to design for low latency writes globally and high availability. What should the Database Engineer do?
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
Change the instance configuration to a multi-region configuration like nam3 (us-central1, us-east1, us-west1) and configure a dedicated write region.
Option C is correct because a multi-region configuration like nam3 (us-central1, us-east1, us-west1) with a dedicated write region provides low-latency writes globally by using Google's managed replication and automatic failover. This design ensures high availability and meets the 10x write traffic increase without sacrificing write performance, as writes are processed in the designated write region and asynchronously replicated to other regions.
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.
- ✗
Shard the database across multiple regional instances based on user geography.
Why it's wrong here
Sharding across instances complicates schema and transactions, and Spanner multi-region is the recommended approach.
- ✗
Create read replicas in other regions to offload read traffic and keep writes in the primary region.
Why it's wrong here
Read replicas do not help with write latency or write capacity.
- ✓
Change the instance configuration to a multi-region configuration like nam3 (us-central1, us-east1, us-west1) and configure a dedicated write region.
Why this is correct
Multi-region configurations provide low-latency writes by placing processing close to users and ensure high availability.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Increase the number of nodes in the existing regional instance to handle the increased write capacity.
Why it's wrong here
This only scales within one region; write latency from other regions will still be high.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse scaling nodes (Option D) with geographic distribution, or assume read replicas (Option B) can handle write scaling, when in fact Cloud Spanner requires a multi-region configuration to achieve both global write low latency and high availability.
Detailed technical explanation
How to think about this question
Cloud Spanner's multi-region configurations use a single write region (leader) and multiple read-only witness or read regions, with synchronous replication within the write region and asynchronous replication to other regions via Paxos-based consensus. The dedicated write region ensures strong consistency for writes, while read regions can serve stale reads with low latency, and automatic failover to another region (if configured) maintains availability during regional outages.
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
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FAQ
Questions learners often ask
What does this PCDE question test?
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: Change the instance configuration to a multi-region configuration like nam3 (us-central1, us-east1, us-west1) and configure a dedicated write region. — Option C is correct because a multi-region configuration like nam3 (us-central1, us-east1, us-west1) with a dedicated write region provides low-latency writes globally by using Google's managed replication and automatic failover. This design ensures high availability and meets the 10x write traffic increase without sacrificing write performance, as writes are processed in the designated write region and asynchronously replicated to other regions.
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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Same concept, more angles
1 more ways this is tested on PCDE
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. A global gaming company uses Cloud Spanner for user profiles and game state. They have a single-region instance in us-central1. Recently, they launched in Europe and notice high latency for European users. They also need to ensure data locality compliance (GDPR). The database is heavily written with throughput spikes. They want to minimize latency without sacrificing write throughput. They consider adding a secondary index on region column. What is the best course of action?
hard- A.Shard the database by region into separate Spanner instances.
- B.Use Cloud CDN to cache read data.
- C.Create a read-only replica in Europe using Cloud Spanner's read replica feature.
- ✓ D.Create a multi-region configuration spanning US and Europe, and modify application to read from closest region.
Why D: Option D is correct because a multi-region Spanner configuration with regional endpoints allows the application to read from the closest region, reducing latency for European users while maintaining strong consistency and write throughput. Spanner's multi-region configurations use synchronous replication across regions, ensuring GDPR compliance by keeping European user data within Europe for reads, and the write throughput is not sacrificed because all writes are committed to the primary region and replicated asynchronously to other regions.
Last reviewed: Jun 11, 2026
This PCDE 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 PCDE exam.
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