Cloud Sql Cross Region Dr Switchover Failover Topology

What the Solution Is

In Cloud SQL Enterprise Plus, advanced disaster recovery relies on designating a cross-region read replica as a designated disaster recovery (DR) replica (configured with the cascadable-replica flag). This architecture uses asynchronous replication across regions to decouple cross-region network latency from production transactions while supporting seamless switchover and failover workflows.

How It Meets the Requirements

• Write latency preservation: Cross-region data replication is fully asynchronous, ensuring that transaction commits on the primary instance are not blocked by inter-region network round-trips.
• Zero-data-loss DR drills: Cloud SQL supports the switchover operation for drills. During a switchover, the primary instance transitions to read-only mode, transaction logs catch up until replication lag reaches zero, and the DR replica is promoted to primary with zero data loss (RPO = 0).
• Disaster mitigation: During an actual regional disaster, executing a replica failover immediately promotes the designated DR replica to primary without waiting for the unavailable primary region to respond.
• Automated traffic routing: Cloud SQL automatically manages a DNS write endpoint that dynamically updates its DNS resolution to point to the newly promoted primary instance across both switchover and replica failover events.

Key Advantages and Capabilities

• Automated topology reversal: After a switchover or when an old primary recovers after failover, Cloud SQL automatically reconfigures the former primary as a replica without requiring manual rebuilds.
• Consistent network endpoints: Database clients connect via a single stable DNS write endpoint, removing the need for manual connection string reconfigurations across microservices.
• Cascading topology support: Cascadable cross-region replicas allow provisioning additional local read replicas in the secondary region without multiplying inter-region bandwidth consumption.

Why This Is Optimal

This configuration balances low write latency during everyday operations with strict RPO compliance during planned maintenance and drill testing, while offering rapid RTO during actual regional failure events.