- A
Use a multi-region configuration with default leader preference set to the region where the application runs.
Why wrong: Multi-region configurations introduce higher write latency and eventual consistency, which may not be optimal for low-latency reads.
- B
Use a regional instance with read replicas in the same region.
Regional instances with read replicas in the same region provide low-latency reads with strong consistency.
- C
Use a single-region instance and configure the leader preference to the application's zone.
Why wrong: Leader preference is only available in multi-region configurations, not single-region.
- D
Use a single-region instance and enable read-only replicas in multiple zones.
Why wrong: Cloud Spanner does not support read-only replicas; all replicas can serve reads and writes.
Quick Answer
The correct choice is a regional instance with read replicas in the same region, as this configuration minimizes Cloud Spanner read latency for applications running in a single Google Cloud region. By keeping all data and replicas within one region, network round-trips are drastically reduced, allowing strongly consistent reads to be served without any cross-region hops. On the Google Professional Cloud Database Engineer exam, this question tests your understanding of how Spanner’s regional versus multi-region configurations impact latency for read-heavy workloads—a common trap is assuming that adding more replicas across regions automatically improves read speed, when in fact it increases latency due to geographic distance. Remember the memory tip: “Same region, same speed; cross region, cross your fingers.”
PCDE Monitor and optimize database performance Practice Question
This PCDE practice question tests your understanding of monitor and optimize database performance. 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 team is deploying a new application on Google Kubernetes Engine (GKE) that uses Cloud Spanner. They want to minimize latency for read operations. Which Spanner configuration should they use?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"minimum / minimize"Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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
Use a regional instance with read replicas in the same region.
Option B is correct because a regional instance with read replicas in the same region provides the lowest read latency for applications running in that region. Cloud Spanner's regional configuration keeps all data and replicas within a single Google Cloud region, minimizing network round-trips. Read replicas in the same region can serve strongly consistent reads without cross-region hops, which is optimal for latency-sensitive workloads.
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.
- ✗
Use a multi-region configuration with default leader preference set to the region where the application runs.
Why it's wrong here
Multi-region configurations introduce higher write latency and eventual consistency, which may not be optimal for low-latency reads.
- ✓
Use a regional instance with read replicas in the same region.
Why this is correct
Regional instances with read replicas in the same region provide low-latency reads with strong consistency.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use a single-region instance and configure the leader preference to the application's zone.
Why it's wrong here
Leader preference is only available in multi-region configurations, not single-region.
- ✗
Use a single-region instance and enable read-only replicas in multiple zones.
Why it's wrong here
Cloud Spanner does not support read-only replicas; all replicas can serve reads and writes.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that multi-region configurations with leader preference reduce read latency, when in fact leader preference only affects write commit latency, not read latency, and multi-region setups inherently add cross-region latency for reads.
Detailed technical explanation
How to think about this question
Cloud Spanner uses a synchronous replication model where all writes must be acknowledged by a majority of replicas in a Paxos group. For reads, Spanner can serve strongly consistent reads from any replica that has the latest data, but in a multi-region setup, the closest replica may still require cross-region communication to confirm freshness. Regional instances avoid this by keeping all replicas within the same region, ensuring that read requests can be served by a local replica with minimal latency. In practice, for read-heavy workloads, a regional configuration can reduce p99 read latency by 50-80% compared to a multi-region setup.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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.
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FAQ
Questions learners often ask
What does this PCDE question test?
Monitor and optimize database performance — This question tests Monitor and optimize database performance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a regional instance with read replicas in the same region. — Option B is correct because a regional instance with read replicas in the same region provides the lowest read latency for applications running in that region. Cloud Spanner's regional configuration keeps all data and replicas within a single Google Cloud region, minimizing network round-trips. Read replicas in the same region can serve strongly consistent reads without cross-region hops, which is optimal for latency-sensitive workloads.
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.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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