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Difficulty: HardDisaster Recovery Strategies

A company hosts a critical customer portal on AWS. The application tier consists of Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer. The stateful database tier runs on Amazon Aurora PostgreSQL in the us-east-1 Region. Static assets are stored in an Amazon S3 bucket. The SysOps Administrator must implement a disaster recovery (DR) strategy in the us-west-2 Region that achieves a Recovery Point Objective (RPO) of less than 55 minutes and a Recovery Time Objective (RTO) of less than 1515 minutes, while minimizing ongoing idle resource costs. Which strategy meets these requirements?

  1. A
    Create an Amazon Aurora PostgreSQL cross-region read replica in us-west-2. Set up Amazon S3 Cross-Region Replication (CRR) to replicate assets. Configure Amazon Route 53 DNS Failover to route traffic to us-west-2, which will automatically promote the read replica to a primary write cluster and redirect database traffic during a failover event.
  2. B
    Configure Amazon S3 Cross-Region Replication (CRR) from the us-east-1 bucket to a new bucket in us-west-2, ensuring versioning is enabled on the source bucket and disabled on the destination bucket to reduce storage costs. Set up hourly Aurora DB cluster snapshots with AWS Backup and copy them to us-west-2. During a disaster, restore the database from the copied snapshot and update DNS records.
  3. Configure an Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2 containing a single Aurora Serverless v2 DB instance configured with minimum capacity. Enable Amazon S3 Cross-Region Replication (CRR) with S3 Versioning enabled on both buckets. Deploy the application tier in us-west-2 using AWS CloudFormation with the Auto Scaling group desired capacity set to 00. During a disaster, promote the secondary DB cluster and update the CloudFormation stack to scale the application instances.Answer
  4. D
    Deploy an active-active multi-region configuration with identical running Aurora DB clusters in both regions. Configure Amazon Route 53 latency-based routing with a DNS record Time to Live (TTL) of 3030 minutes to manage traffic distribution and failover.

Answer

The correct strategy uses an Amazon Aurora Global Database with a minimum-capacity Aurora Serverless v2 instance in the secondary region, S3 Cross-Region Replication with versioning enabled on both buckets, and an application Auto Scaling group in the secondary region with desired capacity set to 00 that is scaled up during a disaster.
The correct strategy utilizes Amazon Aurora Global Database to achieve sub-second cross-region replication, easily satisfying the 55-minute RPO. Operating a single Aurora Serverless v2 DB instance configured at minimum capacity in the recovery region minimizes database idle cost. S3 replication is properly enabled with versioning on both source and destination buckets. The application tier's Auto Scaling group is set to a desired capacity of 00 to eliminate EC2 costs until a failover is declared. Scaling up the instances and promoting the database cluster during a disaster can be completed in a few minutes, which satisfies the 1515-minute RTO.

Step-by-Step Solution

1
Determine the database recovery method that meets the RPO of less than 55 minutes and the RTO of less than 1515 minutes at minimum cost.
Amazon Aurora Global Database provides physical, sub-second cross-region replication lag (satisfying the 55-minute RPO) and allows cluster promotion in under 11 minute (satisfying the database RTO). Deploying a single Serverless v2 instance with minimum capacity (0.5 ACU) minimizes idle running costs.
Restoring from backups cannot meet the 55-minute RPO, and a cross-region read replica cannot automate failover via Route 53.
2
Evaluate S3 bucket replication requirements.
S3 Cross-Region Replication (CRR) must have S3 Versioning enabled on both the source bucket and the destination bucket.
Replication will fail to initiate if versioning is disabled on the destination bucket.
3
Identify the compute tier configuration and DNS failover timing.
Keep the standby application tier scaled down to 00 EC2 instances using CloudFormation. During disaster recovery, promote the secondary Aurora cluster and scale up the ASG. Ensure DNS failover policies do not use high TTLs (like 3030 minutes) that would delay traffic redirection beyond the 1515-minute RTO.
This pilot-light/warm standby compute model ensures zero running compute costs when idle, while still allowing the system to scale and redirect traffic within the 1515-minute RTO.

Key Concept

Disaster Recovery Strategies
Estimated Time:2m 30s
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Disaster Recovery Strategies

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