Quick Answer
The answer is to change the default leader option to 'NEAREST'. This is correct because Cloud Spanner’s multi-region configuration uses a single leader replica to coordinate writes, and when clients are geographically distant from that leader, every write incurs a long network round-trip for confirmation. By setting the default leader option to 'NEAREST', Spanner dynamically assigns the leader to the region closest to the majority of write requests, directly reducing write latency for far-away clients. On the Google Professional Cloud Database Engineer exam, this scenario tests your understanding of leader placement strategies and how they impact performance in distributed databases; a common trap is assuming you must manually reconfigure regions or add read replicas, which do not affect write latency. Remember the mnemonic: "NEAREST leader, fastest writer" — the leader follows the writes, not the other way around.
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 company runs a Cloud Spanner database with a multi-region configuration. They notice that write latency is higher than expected for clients in a region far from the leader region. What action should be taken to reduce write latency?
Reduce the number of replicas
Why wrong: Fewer replicas would not reduce latency and could affect availability.
Use directed reads
Why wrong: Directed reads only affect read requests, not writes.
Change the default leader option to 'NEAREST'
This places the leader in the nearest region, reducing write latency for that region.
Enable follower reads for writes
Why wrong: Follower reads are for reads only; writes must go to the leader.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Change the default leader option to 'NEAREST'
Option C is correct because changing the default leader option to 'NEAREST' allows Cloud Spanner to dynamically assign the leader replica to the region closest to the majority of write requests, reducing the network round-trip time for clients far from the original leader region. This directly addresses the high write latency caused by geographic distance, as writes must be confirmed by the leader before committing.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Reduce the number of replicas
Why it's wrong here
Fewer replicas would not reduce latency and could affect availability.
Use directed reads
Why it's wrong here
Directed reads only affect read requests, not writes.
Change the default leader option to 'NEAREST'
Why this is correct
This places the leader in the nearest region, reducing write latency for that region.
Related concept
Read the scenario before looking for a memorised answer.
Enable follower reads for writes
Why it's wrong here
Follower reads are for reads only; writes must go to the leader.
Common exam traps
The trap here is that candidates confuse directed reads (which reduce read latency) with leader placement options (which reduce write latency), or incorrectly assume that reducing replicas or using follower reads can improve write performance.
Detailed technical explanation
In Cloud Spanner, the leader replica is responsible for sequencing all writes in a region via the Paxos protocol; by default, the leader is fixed to a specific region. The 'NEAREST' leader option uses a dynamic leader placement algorithm that considers the geographic origin of write requests and network latency, automatically moving the leader to the region with the highest write volume or closest proximity, which can significantly reduce commit latency for distributed clients. This is particularly effective in multi-region configurations where write traffic is asymmetric across regions.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Monitor and optimize database performance — This question tests Monitor and optimize database performance — Read the scenario before looking for a memorised answer..
The correct answer is: Change the default leader option to 'NEAREST' — Option C is correct because changing the default leader option to 'NEAREST' allows Cloud Spanner to dynamically assign the leader replica to the region closest to the majority of write requests, reducing the network round-trip time for clients far from the original leader region. This directly addresses the high write latency caused by geographic distance, as writes must be confirmed by the leader before committing.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 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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