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

A credit scoring company hosts its core risk evaluation platform on AWS. The application runs on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer in the us-east-1 Region. The database tier uses an Amazon Aurora PostgreSQL DB cluster. The company needs to design a disaster recovery (DR) plan in the us-west-2 Region to handle a full region outage. The DR solution must achieve a Recovery Point Objective (RPO) of 5 minutes and a Recovery Time Objective (RTO) of 30 minutes while minimizing ongoing running costs.

Which solution meets these requirements with the lowest cost?

  1. Create an Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2 containing zero DB instances. Copy the application AMIs to us-west-2. Deploy an AWS CloudFormation template that provisions the Application Load Balancer and the Auto Scaling group in us-west-2, and add a DB instance to the secondary Aurora cluster during a failover event.Answer
  2. B
    Create an Amazon Aurora Global Database with a secondary DB cluster in us-west-2 containing a running DB instance of the same size. Deploy the Application Load Balancer and a scaled-down Auto Scaling group running at minimum capacity in us-west-2 to enable rapid traffic redirection during a failover event.
  3. C
    Configure an Amazon RDS for PostgreSQL cross-region read replica in us-west-2. Set up Amazon Route 53 latency-based routing to automatically promote the read replica to primary and redirect all client application traffic to us-west-2 if the primary region becomes unavailable.
  4. D
    Configure daily Amazon Aurora DB cluster snapshots and copy them to an Amazon S3 bucket in us-west-2, transitioning them immediately to S3 Glacier Flexible Retrieval. In the disaster recovery region, write an automation script to retrieve the snapshot, restore the DB cluster, and launch the compute tier.

Answer

Create an Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2 containing zero DB instances. Copy the application AMIs to us-west-2. Deploy an AWS CloudFormation template that provisions the Application Load Balancer and the Auto Scaling group in us-west-2, and add a DB instance to the secondary Aurora cluster during a failover event.
The correct option implements a Pilot Light strategy using Amazon Aurora Global Database. Aurora Global Database replicates storage updates with typical replication lag of less than one second, satisfying the 5-minute RPO. By configuring the secondary cluster in the recovery region with zero DB instances, the compute cost is zero during normal operations. The 30-minute RTO provides ample time to add a DB instance to the secondary cluster and deploy the load balancer and Auto Scaling group via AWS CloudFormation templates.

Step-by-Step Solution

1
Analyze RPO requirements and select replication technology.
Amazon Aurora Global Database provides physical, storage-level replication with lag under 1 second, meeting the 5-minute RPO.
Standard daily backups or manual cross-region copies could violate the low RPO under peak write workloads.
2
Analyze RTO requirements and determine the pilot light compute state.
An RTO of 30 minutes allows sufficient time to provision compute resources dynamically rather than keeping them active.
Starting an Aurora DB instance in a headless secondary cluster and deploying EC2 instances via CloudFormation takes approximately 10 to 15 minutes, well within the 30-minute limit.
3
Evaluate costs of different active states in the secondary region.
Maintaining a secondary cluster with zero DB instances and using on-demand infrastructure provisioning via templates minimizes compute costs.
Warm Standby solutions require running continuous standby compute resources, which increases ongoing operational costs unnecessarily.

Key Concept

Pilot Light Disaster Recovery with Aurora Global Database
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Topics

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

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