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Question

Difficulty: HardEnhancing Reliability and Disaster Recovery

An enterprise runs a critical medical imaging application across multiple AWS accounts in an AWS Organization. The core database is an Amazon Aurora MySQL global database, with the primary cluster in us-east-1 and a secondary cluster in us-west-2. The application layer runs on Amazon Elastic Container Service (Amazon ECS) tasks on AWS Fargate behind Application Load Balancers (ALBs) in both regions. The application's DNS domain, imaging.internal.example.com, is hosted in a Route 53 private hosted zone (PHZ) in a shared services account. The PHZ is associated with the application VPCs in both regions. A Solutions Architect needs to enhance the disaster recovery (DR) capability to achieve a Recovery Time Objective (RTO) of less than 15 minutes and a Recovery Point Objective (RPO) of less than 2 minutes. The failover process must be fully automated, including the routing of internal traffic to the active region during an outage in us-east-1. Which combination of actions should the Solutions Architect take to meet these requirements? (Select TWO.)

  1. Configure a Route 53 health check that monitors a CloudWatch alarm tracking the HealthyHostCount metric of the primary Application Load Balancer. In the private hosted zone, configure failover routing records for the application domain, associating the primary record with this health check.Answer
  2. Configure an Amazon EventBridge rule in the primary region to trigger when the CloudWatch alarm monitoring the Application Load Balancer health transitions to the ALARM state. Target an AWS Lambda function that invokes the RDS failover-global-cluster API to promote the secondary database cluster.Answer
  3. C
    Create standard Route 53 HTTP health checks pointing directly to the private IP addresses of the primary Application Load Balancer, and enable evaluate target health on the alias records.
  4. D
    Create a new private hosted zone with the same domain name in the secondary region's VPC, and configure Route 53 active-active weighted routing records without health checks to distribute traffic evenly.
  5. E
    Implement an AWS Backup schedule to take incremental database snapshots every 15 minutes, copy them to the secondary region, and write an AWS Lambda function to restore the cluster during a failover.

Answer

The correct actions are to configure a Route 53 health check that monitors a CloudWatch alarm tracking the HealthyHostCount metric of the primary Application Load Balancer, and to configure an Amazon EventBridge rule that triggers an AWS Lambda function to promote the secondary database cluster using the failover-global-cluster API call.
The correct options implement a fully automated active-passive failover. In a private hosted zone, standard Route 53 health checks cannot directly probe internal resources; instead, a CloudWatch alarm based on ALB health is monitored by Route 53. To fail over the database, an EventBridge rule catches the alarm state transition and triggers a Lambda function to promote the secondary Aurora cluster using the RDS failover-global-cluster API.

Step-by-Step Solution

1
Address private network routing failover by creating a CloudWatch alarm that tracks the HealthyHostCount metric of the primary ALB.
A metric-based trigger is established in the primary region to detect application layer failure.
Route 53 cannot probe private IP addresses directly from its public health checkers, so monitoring a CloudWatch alarm is required for Route 53 Private Hosted Zone failover.
2
Configure a Route 53 health check linked to the CloudWatch alarm, and create primary/secondary failover records in the private hosted zone.
Internal DNS queries resolve to the secondary ALB if the primary ALB becomes unhealthy.
This automates traffic redirection to the secondary region within minutes, contributing to the sub-15-minute RTO goal.
3
Configure an EventBridge rule that listens to the state change of the primary ALB CloudWatch alarm and triggers an AWS Lambda function.
An automated failover script is invoked upon detecting a primary region outage.
Automating the database promotion is necessary to achieve near-zero RPO and low RTO without manual intervention.
4
Use the AWS SDK inside the Lambda function to execute the failover-global-cluster API against the Aurora Global Database.
The secondary cluster is promoted to a standalone primary cluster.
Aurora Global Database replication has an RPO of less than 1 second, and promoting the secondary cluster takes less than a few minutes, satisfying the DR objectives.

Key Concept

Multi-region disaster recovery automation using Route 53 private hosted zones and Aurora Global Database failover mechanisms.
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Topics

Enhancing Reliability and Disaster Recovery