Examkin

Question

Difficulty: EasyEnhancing Reliability and Disaster Recovery

An enterprise has a web application running in a single AWS Region. The application uses an Amazon RDS for PostgreSQL database and an Auto Scaling group of Amazon EC2 instances behind an Application Load Balancer. The Solutions Architect needs to configure a Pilot Light disaster recovery (DR) strategy in a secondary Region. The company requires a Recovery Point Objective (RPO) of 1 hour and a Recovery Time Objective (RTO) of 4 hours. Which of the following actions should the Solutions Architect take to meet these requirements at the lowest cost? (Select TWO.)

  1. Create a cross-Region Read Replica of the primary database instance in the secondary Region.Answer
  2. Deploy the application tier using AWS CloudFormation in the secondary Region, keeping the Auto Scaling group's desired capacity set to zero.Answer
  3. C
    Use AWS Backup to take daily snapshots of the database, copy them to the secondary Region, and restore the database from the snapshots during failover.
  4. D
    Configure an Amazon Route 53 active-active weighted routing policy directing traffic to both regions without attaching health checks to the records.
  5. E
    Create a Route 53 Private Hosted Zone for the database domain name in the primary Region VPC, but do not associate it with the secondary Region VPC.

Answer

Create a cross-Region Read Replica of the primary database instance in the secondary Region, and deploy the application tier using AWS CloudFormation in the secondary Region, keeping the Auto Scaling group's desired capacity set to zero.
The correct architecture uses a Pilot Light DR pattern. This is accomplished by setting up a cross-Region Read Replica of the RDS database to maintain continuous replication (RPO < 1 hour) and preparing the application environment using CloudFormation templates with the Auto Scaling group scaled to zero capacity. This ensures no compute costs are incurred in the disaster recovery region until a failover event occurs, which can be accomplished well within the 4-hour RTO window.

Step-by-Step Solution

1
Select a replication mechanism that supports an RPO of 1 hour for the database tier.
Establish a cross-Region Read Replica of the RDS PostgreSQL database in the secondary Region to enable continuous asynchronous replication.
This keeps data replication latency very low (typically seconds to minutes) and easily satisfies the 1-hour RPO requirement.
2
Determine the application tier deployment strategy to meet the 4-hour RTO at the lowest cost.
Deploy the compute infrastructure using CloudFormation with the Auto Scaling group desired capacity set to 0.
This implements the 'pilot light' pattern where the application tier does not consume active running resources (saving costs) but can be scaled up within minutes during a failover, meeting the 4-hour RTO.

Key Concept

The Pilot Light disaster recovery pattern uses continuous database replication with dormant application infrastructure to achieve low RTO and RPO objectives cost-effectively.
Estimated Time:2m 0s
Rate this question

Topics

Enhancing Reliability and Disaster Recovery