PCDE Practice Question: Deploy scalable and highly available databases in Google Cloud
A company uses Cloud Spanner in a multi-region configuration with the leader region in us-central1. They want to improve write latency for users in Europe. The application's writes are latency-sensitive and must be strongly consistent. Which action should the engineer take?
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 leader region to a European region, such as europe-west1.
In Spanner multi-region, the leader region determines where writes are committed. To reduce write latency for European users, set the leader region to a European region (e.g., europe-west1). All writes will be committed in that region, reducing round-trip time for European clients. This does not affect consistency; Spanner still provides strong consistency globally. Adding more read replicas in Europe does not affect write latency. Moving the application to Cloud SQL or Bigtable does not provide the same global strong consistency or may not meet requirements.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Add more read-only replicas in the European region.
Why it's wrong here
Read-only replicas reduce read latency but do not affect write latency. Writes still go to the leader region.
- ✗
Use a regional Spanner instance in Europe and replicate data asynchronously to the multi-region instance.
Why it's wrong here
Asynchronous replication would break strong consistency and Spanner's guarantees. Spanner does not support this configuration.
- ✗
Migrate the workload to Cloud Bigtable with replication.
Why it's wrong here
Bigtable does not provide strong consistency across regions; it offers eventual consistency. The application requires strong consistency.
- ✓
Change the leader region to a European region, such as europe-west1.
Why this is correct
Setting the leader region to Europe ensures writes are committed in Europe, reducing write latency for European users while maintaining strong consistency.
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