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

An energy trading platform hosts its core transaction processing application in the us-east-1 Region. The architecture consists of an Auto Scaling group of Amazon EC2 instances behind an Application Load Balancer (ALB), and a Multi-AZ Amazon RDS for PostgreSQL DB instance. The company needs to design a disaster recovery (DR) solution in the us-west-2 Region. The solution must achieve a Recovery Time Objective (RTO) of 30 minutes and a Recovery Point Objective (RPO) of 5 minutes while minimizing ongoing running costs. Which strategy meets these requirements?

  1. Deploy an ALB and an Auto Scaling group in the us-west-2 Region with its desired capacity set to 0. Create an RDS for PostgreSQL cross-region read replica in us-west-2. In the event of a disaster, promote the read replica to a standalone DB instance, scale up the Auto Scaling group to its desired capacity, and update the Route 53 DNS records to point to the secondary ALB.Cevap
  2. B
    Deploy a duplicate application tier in the us-west-2 Region with the Auto Scaling group running at minimum capacity. Create an RDS for PostgreSQL cross-region read replica in us-west-2. Configure Amazon Route 53 latency-based routing to distribute user traffic between both regions, relying on Route 53 to automatically stop routing traffic to the primary region if it becomes unhealthy.
  3. C
    Deploy an ALB and an Auto Scaling group in the us-west-2 Region with its desired capacity set to 0. Schedule AWS Backup to take hourly database snapshots, copy them to us-west-2, and transition them to Amazon S3 Glacier Flexible Retrieval. In the event of a disaster, initiate a standard retrieval of the snapshot, restore the RDS database, scale up the Auto Scaling group, and update DNS records.
  4. D
    Deploy an ALB and an Auto Scaling group in the us-west-2 Region with its desired capacity set to 0. Create an RDS for PostgreSQL cross-region read replica in us-west-2. Configure the primary Application Load Balancer to automatically failover and direct database write operations to the us-west-2 read replica if the primary RDS instance goes offline.

Cevap

Deploy an ALB and an Auto Scaling group in the us-west-2 Region with its desired capacity set to 0, create an RDS read replica in the secondary region, promote the replica to standalone during disaster recovery, scale up the Auto Scaling group, and update Route 53 DNS records.
The correct strategy uses an RDS cross-region read replica to satisfy the 5-minute RPO via continuous asynchronous replication. Ongoing costs are minimized by using a Pilot Light strategy, keeping the secondary Auto Scaling group at zero capacity during normal operations. During a disaster, promoting the replica and scaling up the Auto Scaling group allows full system recovery within the 30-minute RTO.

Adım Adım Çözüm

1
Set up database replication using an Amazon RDS for PostgreSQL cross-region read replica in the secondary region (us-west-2).
Database changes are replicated asynchronously with sub-second/sub-minute lag, meeting the 5-minute RPO.
Asynchronous cross-region replication is required to achieve the strict RPO without impacting the write latency of the primary database in the us-east-1 Region.
2
Deploy the application load balancer and the Auto Scaling group in the secondary region with the desired capacity set to 0.
The infrastructure is provisioned but runs at zero compute cost during normal operations, meeting the cost optimization requirement.
This implements the Pilot Light recovery pattern, which ensures infrastructure configuration is ready to scale up immediately without incurring continuous EC2 instance costs.
3
Define the disaster recovery failover workflow to promote the read replica to a standalone DB, scale up the Auto Scaling group, and update DNS records to point to the secondary ALB.
The application becomes fully functional in the secondary region within the 30-minute RTO limit.
Promoting an RDS read replica takes only a few minutes, and EC2 instances in the Auto Scaling group can boot and register with the ALB quickly, allowing recovery within the 30-minute target.

Anahtar Kavram

Using a cross-region RDS read replica combined with a Pilot Light application tier (zero-capacity Auto Scaling group) allows an architecture to meet low RTO and RPO requirements while keeping idle running costs to a minimum.
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Konular

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

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