A company has a Spanner instance for global transactions. They need to ensure reliability during a regional outage. What is the best approach?
Automatic failover and read scalability.
Why this answer
Spanner's multi-region configuration with read-only replicas provides global transactional consistency and automatic failover without manual intervention. Read-only replicas can serve reads locally and, in the event of a regional outage, one can be promoted to a read-write replica to maintain availability. This approach ensures reliability during a regional outage while preserving Spanner's strong consistency guarantees.
Exam trap
Google Cloud often tests the misconception that multiple independent instances (Option B) are needed for cross-region resilience, when in fact Spanner's multi-region configuration with read-only replicas provides built-in global high availability without application changes.
How to eliminate wrong answers
Option A is wrong because Spanner's zone-level resilience does not protect against a full regional outage; backup/restore is a disaster recovery mechanism with significant RTO/RPO, not a high-availability solution. Option B is wrong because using multiple independent Spanner instances in different regions would require application-level sharding or eventual consistency, breaking Spanner's native strong consistency and global transaction support. Option D is wrong because leader placement only controls which zone holds the leader for a given split, but does not provide read-only replicas or automatic failover across regions for regional outage protection.