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

An e-learning enterprise hosts its online classroom application in the us-east-1 Region. The architecture consists of Amazon EC2 instances in an Auto Scaling group and an Amazon RDS for PostgreSQL DB instance. The company needs to implement a cost-effective cross-Region disaster recovery (DR) solution in the us-west-2 Region. The DR solution must achieve a Recovery Point Objective (RPO) of 5 minutes and a Recovery Time Objective (RTO) of 15 minutes. Which combination of actions should a solutions architect recommend to meet these requirements? (Select TWO.)

  1. Configure an Amazon RDS cross-Region read replica in the secondary Region, and promote the read replica to a primary DB instance during failover.Answer
  2. Deploy a scaled-down, active Auto Scaling group of EC2 instances behind an Application Load Balancer in the secondary Region.Answer
  3. C
    Configure Amazon Route 53 with latency-based routing to automatically redirect application traffic to the secondary Region read replica in the event of an outage.
  4. D
    Deploy a pilot light environment in the secondary Region where EC2 instances are stopped, and copy RDS daily snapshots to Amazon S3 Glacier Flexible Retrieval in the secondary Region.
  5. E
    Configure Amazon RDS Multi-AZ replication to synchronize data between the primary Region and the secondary Region, enabling automatic database failover.

Answer

Configure an Amazon RDS cross-Region read replica in the secondary Region and promote it during failover, combined with deploying a scaled-down, active Auto Scaling group of EC2 instances behind an Application Load Balancer in the secondary Region.
To meet the RPO of 5 minutes, database replication must be continuous. An Amazon RDS cross-Region read replica uses asynchronous replication to keep data synchronized with very low replication lag (usually seconds). Promoting this replica to a primary database instance takes a few minutes, which fits within the 15-minute RTO. To meet the RTO of 15 minutes for the compute tier, a Warm Standby environment is required. Deploying a scaled-down but active Auto Scaling group of EC2 instances behind an Application Load Balancer ensures that resources are already online and ready to quickly scale up to meet production demands without the boot latency associated with starting stopped instances.

Step-by-Step Solution

1
Analyze the RTO and RPO requirements.
The target RPO is 5 minutes and the RTO is 15 minutes, requiring a dynamic replication mechanism and an active or near-active computing environment.
Establishing these targets helps eliminate strategies with high recovery time (such as backup and restore from S3 Glacier) or high data loss.
2
Select the database replication strategy.
Identify that an Amazon RDS cross-Region read replica provides continuous asynchronous replication, keeping the data lag under 5 minutes (RPO), and can be promoted to primary within minutes (RTO).
RDS cross-Region read replicas are the standard way to replicate RDS PostgreSQL databases across Regions asynchronously.
3
Select the application compute strategy.
Determine that a Warm Standby strategy (deploying a scaled-down, active Auto Scaling group behind an ALB in the secondary Region) satisfies the 15-minute RTO because compute instances are already running and can be scaled up immediately.
A Pilot Light strategy with stopped instances would introduce startup delays that could risk breaching the strict 15-minute RTO under load.

Key Concept

Disaster Recovery strategies (Warm Standby vs. Pilot Light) and cross-Region database replication (RDS Read Replicas vs. Multi-AZ).
Estimated Time:2m 0s
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Topics

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

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