RDS MySQL Cross-Region Read Replica for Disaster Recovery
A company is designing a disaster recovery solution for a critical application running on Amazon EC2. The application uses an Amazon RDS for MySQL database. The recovery time objective (RTO) is 15 minutes, and the recovery point objective (RPO) is 1 hour. The primary region is us-east-1, and the secondary region is us-west-2. Which solution meets the requirements with the LOWEST cost?
Quick Answer
The correct choice is a cross-region read replica in us-west-2 with MySQL asynchronous replication, as it meets both the 15-minute RTO and 1-hour RPO at the lowest cost. This solution works because cross-region read replicas use MySQL’s native asynchronous replication to continuously copy data to the secondary region with an RPO typically measured in seconds to minutes, and they can be promoted to a standalone primary instance in minutes, satisfying the RTO without expensive infrastructure. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your ability to distinguish between disaster recovery mechanisms: Multi-AZ is for high availability within a single region, not cross-region DR, while automated backups and DMS lack the real-time replication speed needed for a low RPO. A common trap is assuming Multi-AZ works across regions or that DMS provides sub-minute replication. Memory tip: think “Read Replica for Rapid Recovery” — cross-region read replicas give you the fastest promotion and lowest cost for cross-region DR with MySQL.
⚠ Common exam trap
Many candidates choose Multi-AZ (Option D) thinking it provides cross-region DR, but Multi-AZ is a single-region HA feature with synchronous replication, not a cross-region DR solution, and it cannot meet the requirement for a secondary region.
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 a cross-region read replica in us-west-2 with MySQL asynchronous replication
A cross-region read replica in us-west-2 with MySQL asynchronous replication meets the RPO of 1 hour and RTO of 15 minutes at the lowest cost. Asynchronous replication provides near-real-time data transfer with minimal overhead, and the read replica can be promoted to a standalone primary instance in minutes, satisfying the RTO. This approach avoids the continuous data transfer costs of DMS and the storage costs of Multi-AZ, while automated backups alone cannot meet the RPO.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use AWS Database Migration Service (DMS) for continuous replication to us-west-2
Why it's wrong here
DMS is for migration, not DR, and adds cost.
- ✓
Use a cross-region read replica in us-west-2 with MySQL asynchronous replication
Why this is correct
Read replica provides near real-time replication and fast promotion.
- ✗
Use automated backups and restore to us-west-2 when needed
Why it's wrong here
Restore from backup takes longer than 15 minutes.
- ✗
Use a Multi-AZ deployment in us-east-1 and failover to a standby instance
Why it's wrong here
Multi-AZ is within region, not cross-region DR.
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Same concept, more angles
3 more ways this is tested on SAP-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is designing a disaster recovery (DR) solution for a critical application running on Amazon EC2 instances in a single AWS Region. The DR site will be in a different Region. The application data is stored in an Amazon RDS for MySQL DB instance with Multi-AZ enabled. The Recovery Point Objective (RPO) is 15 minutes, and the Recovery Time Objective (RTO) is 2 hours. Which strategy meets these requirements MOST cost-effectively?
hard- A.Take daily automated snapshots of the RDS DB instance and copy them to the DR Region. In the DR Region, restore the DB instance from the latest snapshot.
- B.Use Amazon Aurora Global Database to replicate data across Regions.
- C.Use AWS Backup to copy backups to the DR Region and set up EC2 Image Builder for application recovery.
- ✓ D.Configure a cross-Region read replica for the RDS MySQL DB instance. In the DR event, promote the read replica to a standalone instance.
Why D: The most cost-effective strategy because a cross-Region read replica for RDS MySQL allows continuous replication with minimal overhead, achieving an RPO of seconds to minutes and an RTO of minutes (promotion time). It avoids the cost of a full Aurora Global Database or the RPO gap from daily snapshots, meeting the 15-minute RPO and 2-hour RTO requirements at lower cost.
Variation 2. A company is designing a disaster recovery solution for a critical application that runs on Amazon EC2 instances in a single AWS Region. The application uses an Amazon RDS for MySQL database. The recovery time objective (RTO) is 1 hour and the recovery point objective (RPO) is 15 minutes. Which combination of steps should the company take to meet these requirements? (Choose THREE.)
medium- ✓ A.Use Amazon Route 53 health checks to monitor the primary application and configure DNS failover to the secondary Region.
- B.Configure a Multi-AZ deployment for the RDS database in the primary Region.
- C.Deploy the application on Amazon Aurora Global Database.
- ✓ D.Create an Amazon Machine Image (AMI) of the EC2 instances and copy it to the secondary Region. Use an Auto Scaling group to launch instances from the AMI.
- ✓ E.Create a cross-Region read replica of the RDS MySQL database in the secondary Region.
Why A: Route 53 health checks can monitor the primary application's endpoint, and DNS failover to a secondary Region enables automatic traffic redirection within minutes, aligning with the 1-hour RTO. This approach provides a simple, stateless failover mechanism without requiring complex routing changes.
Variation 3. A company is designing a new disaster recovery solution for a critical application that runs on Amazon EC2 with an Amazon RDS for MySQL database. The Recovery Time Objective (RTO) is 15 minutes and Recovery Point Objective (RPO) is 1 hour. Which TWO strategies meet these requirements? (Choose TWO.)
hard- ✓ A.Use Amazon Aurora Global Database for the database tier.
- ✓ B.Use a cross-region read replica for RDS and promote it during disaster.
- C.Use EC2 AMI copy to another region and launch instances from the AMI.
- D.Use RDS cross-region snapshots and restore in the DR region.
- E.Configure RDS Multi-AZ in the primary region.
Why A: Amazon Aurora Global Database supports cross-region replication with typical RPO of less than 1 second and RTO of less than 1 minute, easily meeting the 15-minute RTO and 1-hour RPO. The primary region writes are asynchronously replicated to up to five secondary regions, and in a disaster, you can promote a secondary region to full read/write in under a minute.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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