Manage a solution that can span multiple database technologies →mediumMultiple ChoiceObjective-mapped
PCDE Practice Question: Manage a solution that can span multiple database technologies
You have a Cloud Spanner database that needs to be migrated from one region to another. You want to ensure no data loss and minimal downtime. Which approach should you use?
⚠ Common exam trap
Google often tests the misconception that Cloud Spanner supports cross-region read replicas like other databases (e.g., Cloud SQL or MySQL), but Spanner's architecture uses a single regional or multi-region instance configuration with synchronous replication, not promotable replicas.
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
✓
Create a backup of the database and restore it to a new instance in the target region.
Cloud Spanner does not support in-place region changes or read replicas in different regions. The only supported method to migrate a Cloud Spanner database between regions with no data loss and minimal downtime is to create a backup of the database and restore it to a new instance in the target region. This approach ensures a consistent snapshot of the data and allows you to plan the cutover window to minimize downtime.
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 gcloud spanner instances move to change the region of the existing instance.
Why it's wrong here
There is no 'move' command; you must backup and restore to a new instance.
- ✓
Create a backup of the database and restore it to a new instance in the target region.
Why this is correct
Backup/restore is the recommended method for moving a Spanner database between regions.
- ✗
Create a read replica in the target region and promote it after replication catches up.
Why it's wrong here
Spanner does not support cross-region read replicas for migration; it uses backups/restores.
- ✗
Use gcloud command 'gcloud spanner databases export' to export the database to CSV files, then import into the new instance.
Why it's wrong here
Exporting to CSV and then importing is unsuitable for migrating a live Cloud Spanner database between regions with minimal downtime and no data loss, as it necessitates taking the database offline for an extended period during the export and import processes, risking data inconsistency. This method is tempting as it's a valid approach for creating backups or migrating to a different database system where direct instance-to-instance replication isn't feasible.
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