Cloud SQL Disaster Recovery Strategy for Regional Outages

PCA By islever Editorial Last updated

Designing network, storage, and compute resources. Ensuring the reliability of solutions in production (e.g., chaos engineering, penetration testing, and load testing)

Short answer

C Configure the Cloud SQL instance with a cross-region read replica and promote it to a primary instance during a regional outage to meet strict RTO and RPO requirements.

Question

Your ecommerce platform uses a regional Cloud SQL for PostgreSQL database to store critical order information. The business requests a recovery time objective (RTO) of less than 10 minutes and a recovery point objective (RPO) of 2 minutes to ensure business continuity in the event of a full regional outage. You need to design a disaster recovery strategy for the Cloud SQL database that meets the business's strict RTO and RPO requirements. Your design must avoid operational complexity. What should you do?
  1. Schedule hourly automated backups of the Cloud SQL instance to a multi-regional Cloud Storage bucket. In a disaster, restore the latest backup to a new instance in a different region.
  2. Use Database Migration Service to continuously replicate the database to another instance in a different region. In a disaster, redirect application traffic to the replica.
  3. Configure the Cloud SQL instance with a cross-region read replica. In a disaster, promote the read replica to a standalone, primary instance. Correct Answer
  4. Configure the primary instance for high availability (HA). In the event of a regional outage, trigger a failover to the standby instance.

Key Takeaways

The main trap is confusing local High Availability (HA) with regional disaster recovery; HA only protects against zone failure, while cross-region replicas are needed for regional outages.

Designing a Cloud SQL disaster recovery strategy for regional outages requires meeting strict RTO/RPO targets. The recommended solution uses cross-region read replicas to ensure rapid failover and minimal data loss.

Common mistake: Option D is the most common mistake because HA is often associated with 'high availability,' but it does not protect against the loss of an entire region, failing the RTO/RPO constraints for regional disasters.

Expert Analysis

Constraints Analysis The question imposes strict Recovery Time Objective (RTO < 10 minutes) and Recovery Point Objective (RPO < 2 minutes) requirements for a full regional outage. It also explicitly mandates avoiding operational complexity.

Option C is the correct answer. A cross-region read replica in Cloud SQL for PostgreSQL maintains an asynchronous copy of the data in a different region. While replication has some lag, it typically stays within seconds to minutes under normal loads, satisfying the 2-minute RPO. In a disaster, promoting a read replica to a standalone primary instance is a managed operation that takes minutes, easily meeting the 10-minute RTO. This approach avoids the heavy operational overhead of managing custom replication scripts or migration pipelines.

Why other options fail:

  • Option A is incorrect because restoring from hourly backups to Cloud Storage involves significant downtime (RTO will likely exceed 10 minutes due to restore time and configuration) and data loss (RPO could be up to 1 hour).
  • Option B is incorrect because Database Migration Service is primarily designed for one-time migrations or ongoing replication for maintenance windows, not as a high-availability disaster recovery solution with automatic failover capabilities. It introduces unnecessary operational complexity compared to native replicas.
  • Option D is incorrect because High Availability (HA) in Cloud SQL provides a local standby within the same region. It protects against zone failures, not full regional outages. If the entire region goes down, the HA instance goes down with it.

Official Reference

https://cloud.google.com/sql/docs/postgres/configure-replication

This link opens the official vendor documentation in a new tab.

Exam Strategy

When designing disaster recovery solutions, always distinguish between zone-level and region-level failures. For regional outages, local HA is insufficient; you must use cross-region replication mechanisms like read replicas or backup restoration, evaluating them against specific RTO/RPO numeric thresholds.

Frequently Asked Questions

What is the difference between Cloud SQL HA and Cross-Region Replicas?

HA provides a synchronous standby in the same region to survive zone failures. Cross-region replicas provide an asynchronous copy in another region to survive regional outages.

Can I use automated backups for disaster recovery?

Automated backups have too high an RTO and RPO for strict requirements like <10 min RTO and <2 min RPO. They are better suited for long-term retention or less critical workloads.

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Discussion 1 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 1

  1. rkumar16d 👍 1 Answered C
    Google specifically recommends a cross-region read replica as part of a Cloud SQL disaster-recovery plan when you need to survive a regional failure and your RTO/RPO requirements are measured in minutes rather than hours.

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