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

A SaaS company hosts an enterprise human resources (HR) portal in the ap-southeast-2 Region. The architecture consists of Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer, and an Amazon RDS for PostgreSQL database. The company needs to design a disaster recovery (DR) plan in the ap-southeast-1 Region. The DR plan must support a recovery time objective (RTO) of 30 minutes and a recovery point objective (RPO) of 5 minutes, while minimizing ongoing running costs.

Which combination of steps should a solutions architect recommend to meet these requirements? (Select TWO.)

  1. Create an Amazon RDS for PostgreSQL cross-region read replica in the disaster recovery region.Answer
  2. Replicate the application server Amazon Machine Images (AMIs) to the disaster recovery region, and create an Auto Scaling group with a desired capacity of zero.Answer
  3. C
    Deploy a Warm Standby environment by keeping a scaled-down Auto Scaling group of EC2 instances running in the disaster recovery region at all times.
  4. D
    Configure the Application Load Balancer to automatically route write traffic to the cross-region read replica if the primary database fails.
  5. E
    Use Amazon Route 53 latency routing to automatically redirect user requests to the disaster recovery region during a database outage.

Answer

To meet the requirements, the solutions architect must configure an Amazon RDS cross-region read replica in the disaster recovery region and replicate the application AMIs to set up an Auto Scaling group with a desired capacity of zero.
The correct options implement a cost-effective Pilot Light strategy. The RPO of 5 minutes is met by creating an Amazon RDS cross-region read replica, which continuously replicates database transactions asynchronously with minimal lag. The RTO of 30 minutes allows the application tier to remain offline (zero running instances) to minimize costs. In a disaster recovery event, the read replica is promoted to a primary database and the Auto Scaling group is scaled up from zero using the replicated AMIs, completing the entire failover well within the 30-minute window.

Step-by-Step Solution

1
Configure database replication for low RPO.
Create a cross-region read replica of the PostgreSQL DB in the ap-southeast-1 region.
Asynchronous cross-region read replicas satisfy the 5-minute RPO by keeping the recovery database up-to-date with minimal replication lag.
2
Minimize recovery region compute costs.
Copy application AMIs to the target region and deploy an Auto Scaling group set to zero instances.
Setting the capacity to zero ensures no running instances are billed during normal operations, implementing a cost-optimized Pilot Light disaster recovery strategy.
3
Define failover procedures.
Create a runbook to promote the read replica to standalone status and scale the Auto Scaling group capacity up during a disaster.
Promoting a replica and booting EC2 instances from AMIs can be completed well within the 30-minute RTO.

Key Concept

A Pilot Light disaster recovery strategy minimizes running costs by keeping compute capacity scaled to zero while maintaining active, asynchronous database replication via cross-region read replicas to meet low recovery point objectives.
Estimated Time:2m 0s
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Topics

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

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