The requirements specify cross-Region failover with an RPO of 5 minutes and an RTO of 20 minutes for a large (10 TB) database. Achieving a low RPO in a secondary Region typically requires near-continuous replication, not periodic snapshots. Achieving a 20-minute RTO requires that the standby data store already exists in the secondary Region and can be promoted quickly.
A cross-Region read replica provides continuous asynchronous replication from the primary Region to a replica in the secondary Region. This is the standard managed approach for cross-Region disaster recovery for Amazon RDS engines that support read replicas. With a read replica already running in the secondary Region, failover can be accomplished by promoting the replica to a standalone primary database instance. This supports an RTO target like 20 minutes because the data is already present and the promotion operation is typically faster than restoring from a full snapshot, especially at 10 TB scale.
Option B describes creating an RDS Multi-AZ DB cluster in the primary Region and a cross-Region read replica in the secondary Region. Multi-AZ addresses high availability within the primary Region, while the cross-Region replica addresses disaster recovery. The option also includes automation using CloudWatch alarms and a Lambda function to promote the replica when a failure is detected. This supports the required RTO by reducing manual intervention time and supports the RPO by using continuous replication.
Option A is not practical for RPO 5 minutes at 10 TB. Taking and copying snapshots every 5 minutes would be operationally heavy and would not complete within the required window; snapshot creation and cross-Region copy are not designed for such high-frequency near-real-time DR. It also risks missing the RPO due to snapshot completion time.
Option C introduces unnecessary complexity and additional services. Creating a second cluster only at failure time is not compatible with a 20-minute RTO for a 10 TB database, and using DMS for continuous sync is more development and operational work than using native RDS replication. This is not the least overhead or most direct DR design.
Option D is incorrect as stated because cross-Region read replicas are not automatically failed over and promoted by an “automated failover” feature in the way Multi-AZ failover works within a Region. Automated backups do not provide near-real-time cross-Region recovery to meet a 5-minute RPO. The usual approach for cross-Region is to create the replica and then promote it through a controlled process, which can be automated via monitoring and Lambda as in option B.
Therefore, using a cross-Region read replica with automation to promote it provides the necessary RPO/RTO with a managed service approach.
[References:AWS documentation on Amazon RDS cross-Region read replicas for disaster recovery and replica promotion procedures.AWS documentation on Multi-AZ deployments for high availability within a Region and combining Multi-AZ with cross-Region read replicas for DR.AWS best practices for meeting RPO/RTO using continuous replication rather than periodic snapshots for large databases., , , ]
