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

A global e-learning provider hosts its platform on AWS. 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 MySQL Multi-AZ DB instance. The provider needs to implement a disaster recovery (DR) strategy in a secondary AWS Region. The strategy must support a Recovery Time Objective (RTO) of 3 hours and a Recovery Point Objective (RPO) of 10 minutes, while keeping ongoing replication and infrastructure costs to a minimum.

Which combination of actions will meet these requirements? (Select TWO.)

  1. Configure an Amazon RDS for MySQL cross-region read replica in the secondary Region, and promote it to a standalone DB instance during a failover event.Answer
  2. Create and copy an Amazon Machine Image (AMI) of the application servers to the secondary Region, and prepare an AWS CloudFormation template to deploy the Application Load Balancer and Auto Scaling group during a failover.Answer
  3. C
    Deploy a scaled-down Auto Scaling group and an Application Load Balancer in the secondary Region that continuously run at minimum capacity.
  4. D
    Configure Amazon Route 53 latency routing to automatically distribute incoming traffic between the application tiers in both Regions.
  5. E
    Take daily Amazon RDS snapshots, copy them to the secondary Region, and store them in Amazon S3 Glacier Flexible Retrieval to restore the database during a failover.

Answer

Configure an Amazon RDS for MySQL cross-region read replica in the secondary Region, and promote it during failover. Additionally, create and copy an AMI of the application servers, and use an AWS CloudFormation template to deploy the application tier resources during failover.
To satisfy the 10-minute RPO, continuous or near-continuous replication is required. Amazon RDS cross-region read replicas automatically replicate changes asynchronously with very low latency, typically in seconds, meeting the RPO. To meet the 3-hour RTO while minimizing ongoing costs, a Pilot Light strategy is ideal. Keeping pre-built AMIs and deploying the infrastructure via AWS CloudFormation templates on-demand avoids paying for running compute instances and load balancers during normal operations, yet allows full recovery within the 3-hour timeline.

Step-by-Step Solution

1
Select a data replication strategy that meets the 10-minute RPO.
Amazon RDS cross-region read replicas use asynchronous replication with very low replication lag (seconds to minutes), satisfying the 10-minute RPO.
Direct backup methods like daily snapshots would violate the 10-minute RPO.
2
Select a compute strategy that meets the 3-hour RTO while minimizing cost.
Store pre-built AMIs and write AWS CloudFormation templates to provision the load balancer and Auto Scaling group when a disaster is declared.
This Pilot Light strategy avoids any ongoing compute costs for idle servers while allowing full provisioning within the 3-hour window.
3
Avoid warm standby or active-active configurations to respect the cost constraint.
Do not provision running EC2 instances or load balancers in the secondary region prior to failover.
Running inactive or scaled-down infrastructure incurs unnecessary ongoing costs.

Key Concept

Designing a cost-effective Pilot Light disaster recovery strategy using cross-region database replication and on-demand infrastructure provisioning.
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Topics

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

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