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Difficulty: MediumMulti-AZ, Multi-Region Architectures and Disaster Recovery (DR)

A retail banking compliance platform hosts its transaction reporting application in the us-east-1 Region. The application runs on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer, and it uses an Amazon RDS for PostgreSQL Multi-AZ DB instance. The bank wants to establish a disaster recovery (DR) strategy in the us-west-2 Region. The solution must support a Recovery Point Objective (RPO) of 10 minutes and a Recovery Time Objective (RTO) of 15 minutes, while minimizing ongoing running costs. Which solution meets these requirements?

  1. A
    Enable Multi-AZ deployment for the RDS DB instance and designate the us-west-2 Region as the secondary Availability Zone. Deploy an Application Load Balancer and a scaled-down Auto Scaling group with a minimum capacity of 1 in the us-west-2 Region. Configure Route 53 latency routing to route traffic between the Regions.
  2. B
    Create a cross-Region Read Replica of the RDS DB instance in the us-west-2 Region. Deploy a replica Application Load Balancer and an Auto Scaling group with a minimum capacity of 0 in the us-west-2 Region. Configure Route 53 failover routing to point to the active Application Load Balancer, and write an automation script to increase the Auto Scaling group minimum capacity to 2 and promote the read replica during failover.
  3. Create a cross-Region Read Replica of the RDS DB instance in the us-west-2 Region. Deploy a replica Application Load Balancer and a scaled-down Auto Scaling group with a minimum capacity of 1 in the us-west-2 Region. Configure Route 53 failover routing to point to the active Application Load Balancer, and promote the read replica to a standalone DB instance during failover.Answer
  4. D
    Configure the RDS DB instance to perform daily backups and copy the snapshots to an Amazon S3 bucket in the us-west-2 Region using S3 Glacier Flexible Retrieval. In the event of a disaster, initiate an expedited retrieval to restore the database, and deploy the EC2 instances using AWS CloudFormation.

Answer

Create a cross-Region Read Replica of the RDS DB instance in the us-west-2 Region. Deploy a replica Application Load Balancer and a scaled-down Auto Scaling group with a minimum capacity of 1 in the us-west-2 Region. Configure Route 53 failover routing to point to the active Application Load Balancer, and promote the read replica to a standalone DB instance during failover.
The correct strategy is a Warm Standby. To meet the 10-minute RPO, a cross-Region Read Replica is deployed in the us-west-2 Region to continuously replicate data asynchronously. To meet the 15-minute RTO, a replica Application Load Balancer and a scaled-down Auto Scaling group with a minimum capacity of 1 are deployed in the target Region. This ensures that the application is running and can immediately begin accepting traffic when Route 53 failover routing is triggered, while the Auto Scaling group scales up dynamically. During failover, the read replica is promoted to a standalone primary database instance.

Step-by-Step Solution

1
Determine the database replication strategy to satisfy the 10-minute Recovery Point Objective (RPO).
Identify that a cross-Region Read Replica replicates transactions asynchronously with minimal lag (seconds or minutes), which successfully satisfies the 10-minute RPO. Daily backups fail this requirement.
Choosing the correct replication technology is necessary to ensure data loss is kept under the target threshold.
2
Select the appropriate disaster recovery (DR) strategy to satisfy the 15-minute Recovery Time Objective (RTO).
Determine that a Warm Standby strategy (keeping a minimum capacity of 1 running instance in the target Region) is required to meet the 15-minute RTO. A Pilot Light strategy (minimum capacity of 0) takes too long to spin up, configure, and pass load balancer health checks from scratch.
Active but scaled-down services ensure immediate traffic ingestion, which minimizes failover delay.
3
Configure the failover mechanism for DNS routing.
Use Amazon Route 53 with failover routing policies pointing to the primary and secondary Application Load Balancers.
This guarantees that incoming traffic is automatically or manually redirected to the disaster recovery Region during an outage.

Key Concept

Disaster recovery strategy trade-offs (RTO and RPO) and AWS cross-region replication configurations.
Estimated Time:2m 0s
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Topics

Multi-AZ, Multi-Region Architectures and Disaster Recovery (DR)

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