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

A municipal energy utility company hosts its customer billing portal in the eu-west-1 Region. The application tier runs on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer (ALB). The database tier uses an Amazon RDS for PostgreSQL DB instance. The company needs to design a disaster recovery (DR) strategy in the eu-central-1 Region. The solution must achieve a Recovery Time Objective (RTO) of 15 minutes and a Recovery Point Objective (RPO) of 5 minutes, while minimizing ongoing costs. Which architecture should a solutions architect recommend to meet these requirements?

  1. A
    Configure an AWS CloudFormation template to deploy the Application Load Balancer and the EC2 Auto Scaling group on-demand in the secondary region during a failover. Configure an Amazon RDS cross-region read replica in the secondary region. In the event of a disaster, deploy the CloudFormation stack, promote the read replica to a primary database, and update Amazon Route 53 failover records.
  2. B
    Configure an Amazon RDS cross-region read replica in the secondary region. Deploy a scaled-down Auto Scaling group of EC2 instances behind an Application Load Balancer in the secondary region. Configure Amazon Route 53 active-passive failover routing so that the database and application traffic automatically failover to the secondary region without administrative intervention.
  3. Configure an Amazon RDS cross-region read replica in the secondary region. Deploy a scaled-down Auto Scaling group of EC2 instances behind an Application Load Balancer in the secondary region. In the event of a disaster, promote the cross-region read replica to a standalone database instance, scale up the Auto Scaling group, and update Amazon Route 53 failover routing records to point to the secondary Application Load Balancer.Answer
  4. D
    Configure a daily database snapshot and copy it to Amazon S3 Glacier Flexible Retrieval in the secondary region. Create an AWS CloudFormation template to deploy the Application Load Balancer and the EC2 Auto Scaling group. In the event of a disaster, retrieve the snapshot from S3 Glacier, restore it to a new RDS instance, deploy the CloudFormation stack, and update Amazon Route 53.

Answer

Configure an Amazon RDS cross-region read replica in the secondary region, deploy a scaled-down Auto Scaling group of EC2 instances behind an Application Load Balancer in the secondary region, and in the event of a disaster, promote the replica, scale up the Auto Scaling group, and update Route 53 failover routing.
A Warm Standby DR strategy is the most cost-effective solution that satisfies both the 15-minute RTO and 5-minute RPO. The cross-region read replica replicates data asynchronously, keeping the RPO under 5 minutes. The scaled-down Auto Scaling group keeps EC2 costs low while ensuring that virtual machines are pre-provisioned and can be scaled up immediately to meet the RTO. Manual promotion of the RDS read replica is required to make the secondary database active for write operations.

Step-by-Step Solution

1
Establish cross-region database replication to meet the RPO requirement.
Create an Amazon RDS cross-region read replica in the secondary region (eu-central-1) to asynchronously replicate the primary PostgreSQL DB instance.
Asynchronous replication runs continuously, keeping the replication lag to seconds or minutes, which satisfies the 5-minute RPO.
2
Set up the application tier in the recovery region to meet the RTO requirement cost-effectively.
Deploy an Application Load Balancer and a scaled-down Auto Scaling group of EC2 instances in the secondary region.
Keeping a Warm Standby (scaled-down Auto Scaling group and ALB) minimizes ongoing costs while ensuring the core compute infrastructure is already online and ready to scale up within minutes.
3
Orchestrate failover in the event of a primary region outage.
Promote the RDS cross-region read replica to a standalone DB instance, scale up the EC2 Auto Scaling group to production size, and update Route 53 DNS records to point to the secondary ALB.
Promoting the read replica and scaling up the existing compute capacity allows the environment to become fully active and handle production traffic within the 15-minute RTO.

Key Concept

Warm Standby Disaster Recovery Strategy
Estimated Time:1m 30s
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Topics

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

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