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Difficulty: MediumDisaster Recovery Strategies

A financial services provider hosts a critical transaction application in the us-east-1 Region. The architecture consists of an Application Load Balancer, an Auto Scaling group of Amazon EC2 instances, and an Amazon Aurora PostgreSQL database cluster. The provider requires a disaster recovery (DR) solution in the us-west-2 Region with a Recovery Point Objective (RPO) of less than 5 minutes and a Recovery Time Objective (RTO) of less than 15 minutes. The solution must minimize ongoing operational costs.

Which strategy meets these requirements?

  1. Configure an Amazon Aurora Global Database with a secondary cluster in us-west-2 containing a single DB instance. Deploy the Application Load Balancer and an Auto Scaling group in us-west-2 with the desired capacity set to 0. During a disaster, promote the secondary Aurora cluster and scale up the Auto Scaling group.Answer
  2. B
    Configure the Aurora PostgreSQL database cluster as Multi-AZ in us-east-1. Deploy a duplicate Application Load Balancer and Auto Scaling group in us-west-2, and configure Amazon Route 53 active-passive failover to route traffic to us-west-2 if the primary region experiences a service disruption.
  3. C
    Set up an Amazon Aurora Global Database with a secondary cluster in us-west-2. Deploy an Application Load Balancer and Auto Scaling group in both regions, and configure an Amazon Route 53 active-active failover routing policy using latency-based routing to distribute write transactions across both regions.
  4. D
    Schedule database backups using script-based snapshots exported to an Amazon S3 bucket in us-east-1. Configure S3 Cross-Region Replication (CRR) to a bucket in us-west-2 without enabling bucket versioning to save on storage fees. In us-west-2, deploy the compute infrastructure with a standby database ready to restore the snapshots.

Answer

Configure an Amazon Aurora Global Database with a secondary cluster in us-west-2 containing a single DB instance. Deploy the Application Load Balancer and an Auto Scaling group in us-west-2 with the desired capacity set to 0. During a disaster, promote the secondary Aurora cluster and scale up the Auto Scaling group.
The correct strategy uses Aurora Global Database, which offers sub-second replication to us-west-2, meeting the 5-minute RPO requirement. By keeping the secondary cluster active with a single DB instance and using an Auto Scaling group with a desired capacity of 0, the organization minimizes ongoing compute costs in the disaster recovery region. In the event of a disaster, promoting the secondary cluster and scaling up the Auto Scaling group can be completed well within the 15-minute RTO target.

Step-by-Step Solution

1
Analyze RTO and RPO requirements.
The RPO must be less than 5 minutes (data loss limit) and the RTO must be less than 15 minutes (downtime limit).
This determines which data replication mechanism and compute restoration process are acceptable.
2
Evaluate the database replication strategy.
Aurora Global Database replicates data within seconds (RPO < 5 minutes) and can be promoted to a standalone read-write cluster in under a minute (RTO < 15 minutes).
Traditional backup-and-restore or snapshot copy methods take too long to restore, violating the 15-minute RTO.
3
Evaluate the cost minimization strategy for compute resources.
Keeping the secondary Auto Scaling group at a desired capacity of 0 ensures that no EC2 instances are running (and incurring costs) under normal conditions, while remaining deployable via scaling actions during failover.
This meets the pilot light / warm standby principle of keeping infrastructure costs to a minimum in the DR region.

Key Concept

Disaster Recovery Strategies
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Disaster Recovery Strategies

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