AWS Certified SysOps Administrator – Associate — Question 440

A company hosts a web portal on Amazon EC2 instances. The web portal uses an Elastic Load Balancer (ELB) and Amazon Route 53 for its public DNS service.
The ELB and the EC2 instances are deployed by way of a single AWS CloudFormation stack in the us-east-1 Region. The web portal must be highly available across multiple Regions.
Which configuration will meet these requirements?

Answer options

• A. Deploy a copy of the stack in the us-west-2 Region. Create a single start of authority (SOA) record in Route 53 that includes the IP address from each ELB. Configure the SOA record with health checks. Use the ELB in us-east-1 as the primary record and the ELB in us-west-2 as the secondary record.
• B. Deploy a copy of the stack in the us-west-2 Region. Create an additional A record in Route 53 that includes the ELB in us-west-2 as an alias target. Configure the A records with a failover routing policy and health checks. Use the ELB in us-east-1 as the primary record and the ELB in us-west-2 as the secondary record.
• C. Deploy a new group of EC2 instances in the us-west-2 Region. Associate the new EC2 instances with the existing ELB, and configure load balancer health checks on all EC2 instances. Configure the ELB to update Route 53 when EC2 instances in us-west-2 fail health checks.
• D. Deploy a new group of EC2 instances in the us-west-2 Region. Configure EC2 health checks on all EC2 instances in each Region. Configure a peering connection between the VPCs. Use the VPC in us-east-1 as the primary record and the VPC in us-west-2 as the secondary record.

Correct answer: B

Explanation

To achieve multi-Region high availability, a duplicate stack containing the ELB and EC2 instances must be deployed in the secondary Region (us-west-2) because ELBs are regional resources and cannot span across Regions, which rules out Option C and D. Route 53 failover routing with alias A records and health checks (Option B) is the correct way to automatically route traffic to the secondary Region if the primary Region's ELB becomes unhealthy. Option A is incorrect because Start of Authority (SOA) records are used for administrative zone details and cannot be configured for failover routing or alias targets.