A property management portal hosts its application in the us-east-1 Region. The database tier runs on an Amazon RDS for PostgreSQL Multi-AZ DB instance. The application tier consists of Amazon EC2 instances inside an Auto Scaling group behind an Application Load Balancer. The company needs to design a disaster recovery (DR) strategy in the us-west-2 Region with a Recovery Time Objective (RTO) of 2 hours and a Recovery Point Objective (RPO) of 15 minutes. The solution must minimize ongoing operational and infrastructure costs. Which disaster recovery strategy should a solutions architect recommend to meet these requirements?
- Configure a cross-region RDS read replica in the DR region. Save the application server configurations as an Amazon Machine Image (AMI) and store the network infrastructure configurations as an AWS CloudFormation template. During a disaster, deploy the infrastructure from the template, promote the RDS read replica to a standalone database, and scale the application tier.Answer
- BConfigure a cross-region RDS read replica in the DR region. Pre-deploy the application load balancer and the Auto Scaling group in the DR region, running at a minimum capacity of one EC2 instance. During a disaster, promote the RDS read replica and scale out the Auto Scaling group to handle the production traffic.
- CConfigure a cross-region RDS read replica in the DR region. Configure Amazon Route 53 with an active-passive failover routing policy pointing to the primary database in the main region and the read replica in the DR region. In the event of a failure, Route 53 will automatically promote the replica and route all database write traffic to the DR region.
- DConfigure daily snapshots of the primary database and copy them to an Amazon S3 Glacier Flexible Retrieval vault in the DR region. Store the application server backups in S3 Glacier. During a disaster, initiate an expedited retrieval of the snapshots, restore the database, and provision new EC2 instances.
Answer
Configure a cross-region RDS read replica in the DR region. Save the application server configurations as an Amazon Machine Image (AMI) and store the network infrastructure configurations as an AWS CloudFormation template. During a disaster, deploy the infrastructure from the template, promote the RDS read replica to a standalone database, and scale the application tier.
The correct strategy is the Pilot Light pattern. By maintaining a cross-region RDS read replica, the database replication is continuous, satisfying the 15-minute RPO. Storing compute and networking tier configurations as CloudFormation templates and AMIs ensures that no EC2 instances or load balancers are running during normal operations, minimizing ongoing costs. Recreating these resources and promoting the RDS read replica during a failover can easily be completed within the 2-hour RTO.
Step-by-Step Solution
Key Concept
Disaster recovery strategies differ in RTO, RPO, and cost. A Pilot Light strategy keeps the database replication active but compute resources offline, making it highly cost-effective while still meeting moderate recovery time objectives.