AWS Certified Solutions Architect – Professional (SAP-C02) — Question 384

A company hosts a community forum site using an Application Load Balancer (ALB) and a Docker application hosted in an Amazon ECS cluster. The site data is stored in Amazon RDS for MySQL and the container image is stored in ECR. The company needs to provide their customers with a disaster recovery SLA with an RTO of no more than 24 hours and RPO of no more than 8 hours.

Which of the following solutions is the MOST cost-effective way to meet the requirements?

Answer options

• A. Use AWS CloudFormation to deploy identical ALB, EC2, ECS and RDS resources in two regions. Schedule RDS snapshots every 8 hours. Use RDS multi-region replication to update the secondary region's copy of the database. In the event of a failure, restore from the latest snapshot, and use an Amazon Route 53 DNS failover policy to automatically redirect customers to the ALB in the secondary region.
• B. Store the Docker image in ECR in two regions. Schedule RDS snapshots every 8 hours with snapshots copied to the secondary region. In the event of a failure, use AWS CloudFormation to deploy the ALB, EC2, ECS and RDS resources in the secondary region, restore from the latest snapshot, and update the DNS record to point to the ALB in the secondary region.
• C. Use AWS CloudFormation to deploy identical ALB, EC2, ECS, and RDS resources in a secondary region. Schedule hourly RDS MySQL backups to Amazon S3 and use cross-region replication to replicate data to a bucket in the secondary region. In the event of a failure, import the latest Docker image to Amazon ECR in the secondary region, deploy to the EC2 instance, restore the latest MySQL backup, and update the DNS record to point to the ALB in the secondary region.
• D. Deploy a pilot light environment in a secondary region with an ALB and a minimal resource EC2 deployment for Docker in an AWS Auto Scaling group with a scaling policy to increase instance size and number of nodes. Create a cross-region read replica of the RDS data. In the event of a failure, promote the replica to primary, and update the DNS record to point to the ALB in the secondary region.

Correct answer: B

Explanation

Option B is the most cost-effective solution because it utilizes a 'Backup and Restore' disaster recovery approach, which avoids incurring costs for running idle compute or database resources in the secondary region. Copying RDS snapshots every 8 hours satisfies the 8-hour RPO, and deploying the environment using AWS CloudFormation during a disaster can easily be completed within the 24-hour RTO. Options A, C, and D are more expensive because they require pre-provisioning active or standby infrastructure in the secondary region.