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

A software-as-a-service (SaaS) company hosts a global hotel booking platform in the eu-west-1 Region. The application tier runs on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer. The database tier uses an Amazon RDS for PostgreSQL DB instance. The company wants to implement a disaster recovery (DR) strategy in the us-east-1 Region that achieves a recovery point objective (RPO) of 5 minutes and a recovery time objective (RTO) of 30 minutes. Which combination of actions should the solutions architect recommend to meet these requirements at the lowest cost? (Select TWO.)

  1. Create an Amazon RDS cross-region read replica in the secondary region, and promote the replica to a standalone DB instance during a failover event.Answer
  2. Deploy the application infrastructure in the secondary region using AWS CloudFormation, and configure the Auto Scaling group with a desired capacity of 0.Answer
  3. C
    Configure Amazon RDS Multi-AZ DB cluster replication across both the primary and secondary regions to enable automatic database failover.
  4. D
    Configure daily database backups to Amazon S3, replicate them to an Amazon S3 Glacier Flexible Retrieval vault in the secondary region, and restore the database from the backup during failover.
  5. E
    Maintain a continuously running, scaled-down fleet of Amazon EC2 instances in the secondary region to guarantee that the application can immediately handle the full production load.

Answer

Creating an Amazon RDS cross-region read replica and promoting it during failover, along with deploying the secondary application infrastructure using AWS CloudFormation with the Auto Scaling group's desired capacity set to 0.
The correct solution uses a Pilot Light disaster recovery strategy. Creating an Amazon RDS cross-region read replica ensures database replication with an RPO of under 5 minutes, and promoting it to a standalone database during failover satisfies the RTO of 30 minutes. Deploying the application tier using AWS CloudFormation with the Auto Scaling group's desired capacity set to 0 minimizes cost by not running any EC2 instances until a failover is needed, while still allowing the application to be launched within the 30-minute RTO.

Step-by-Step Solution

1
Analyze the RPO requirement (5 minutes) and choose the appropriate database replication mechanism.
An Amazon RDS cross-region read replica is selected, as it replicates asynchronously across regions with very low lag (usually seconds to minutes), satisfying the 5-minute RPO.
A database backup/restore method would fail the RPO, and Multi-AZ cannot span multiple regions.
2
Analyze the RTO requirement (30 minutes) and cost constraint to determine the compute tier strategy.
Choose the Pilot Light strategy by pre-staging the infrastructure with AWS CloudFormation and setting the Auto Scaling group desired capacity to 0.
This avoids running compute resources continuously (saving cost) while ensuring that the EC2 instances can be provisioned and scaled up within the 30-minute window.
3
Combine the database and compute tier actions to form the complete disaster recovery plan.
A cross-region read replica handles the database, and CloudFormation with a desired capacity of 0 handles the compute tier.
This combination satisfies both RPO and RTO requirements at the lowest cost.

Key Concept

Disaster Recovery (DR) patterns in AWS prioritize tradeoffs between RTO, RPO, and cost. A Pilot Light strategy pre-stages infrastructure (such as CloudFormation templates and scaled-down resources) and replicates database data asynchronously to meet low RPO/RTO targets while minimizing compute costs.
Estimated Time:2m 0s
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Topics

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

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