PCDE Practice Question: Deploy scalable and highly available databases in Google Cloud
A company uses Cloud Spanner with a single-region configuration in us-central1. They need to improve disaster recovery to meet an RPO of zero and an RTO of less than 5 seconds across regions. Which three actions should they take? (Choose three.)
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 backup/restore to migrate data from the single-region instance to the new multi-region instance
To achieve RPO=0 and RTO<5s across regions, you need a multi-region Spanner configuration with synchronous replication. You cannot achieve cross-region RPO=0 with a single-region instance. Therefore, you must migrate to a multi-region configuration. The steps include: 1) Create a new multi-region instance (e.g., nam6) with the desired config, 2) Migrate data from the single-region instance to the multi-region instance (e.g., using backup/restore or Dataflow), 3) Update application connection strings to point to the new instance. Optionally, you can perform a rolling migration to minimize downtime. Using cross-region read replicas is not possible for Spanner (Spanner does not have read replicas in the same sense; it uses replica types within an instance).
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 a cross-region read replica to the existing single-region instance
Why it's wrong here
Spanner does not support cross-region read replicas; multi-region is an instance-level configuration.
- ✓
Use backup/restore to migrate data from the single-region instance to the new multi-region instance
Why this is correct
Backup/restore is a reliable way to move data between instances.
- ✗
Enable point-in-time recovery (PITR) with 7-day retention
Why it's wrong here
PITR does not provide cross-region failover with RPO=0 and RTO<5s; it is for point-in-time recovery within a region.
- ✓
Update application connection strings to point to the multi-region instance
Why this is correct
Applications must connect to the new instance to use it.
- ✓
Create a new multi-region Spanner instance with a two-region configuration (e.g., nam6)
Why this is correct
A multi-region instance with synchronous replication provides RPO=0 and automatic failover with RTO<5s.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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