What should a solutions architect recommend to meet these requirements?
Reconfigure the application’s Route 53 record with a latency-based routing policy that load balances traffic between the two ALBs. Create an AWS Lambda function in the backup Region to promote the read replica and modify the Auto Scaling group values. Create an Amazon CloudWatch alarm that is based on the HTTPCode_Target_5XX_Count metric for the ALB in the primary Region. Configure the CloudWatch alarm to invoke the Lambda function.
Create an AWS Lambda function in the backup Region to promote the read replica and modify the Auto Scaling group values. Configure Route 53 with a health check that monitors the web application and sends an Amazon Simple Notification Service (Amazon SNS) notification to the Lambda function when the health check status is unhealthy. Update the application’s Route 53 record with a failover policy that routes traffic to the ALB in the backup Region when a health check failure occurs.
Configure the Auto Scaling group in the backup Region to have the same values as the Auto Scaling group in the primary Region. Reconfigure the application’s Route 53 record with a latency-based routing policy that load balances traffic between the two ALBs. Remove the read replica. Replace the read replica with a standalone RDS DB instance. Configure Cross-Region Replication between the RDS DB instances by using snapshots and Amazon S3.
Configure an endpoint in AWS Global Accelerator with the two ALBs as equal weighted targets. Create an AWS Lambda function in the backup Region to promote the read replica and modify the Auto Scaling group values. Create an Amazon CloudWatch alarm that is based on the HTTPCode_Target_5XX_Count metric for the ALB in the primary Region. Configure the CloudWatch alarm to invoke the Lambda function.
Explanations:
Latency-based routing would distribute traffic between both Regions, which is not suitable since only one Region should be active at a time. Additionally, while the Lambda function promotes the read replica and adjusts Auto Scaling, latency-based routing does not inherently enable failover.
This approach sets up a health check in Route 53 to monitor the application, triggering failover when the primary Region becomes unhealthy. The failover policy in Route 53 and Lambda function to promote the read replica and scale the Auto Scaling group meet the RTO requirement effectively without a costly active-active setup.
Using latency-based routing with equal Auto Scaling settings in both Regions suggests an active-active setup, which the company cannot afford. Cross-Region replication with snapshots and S3 is also slower and does not meet the 15-minute RTO requirement.
Global Accelerator with equal-weighted targets does not facilitate a primary-backup configuration and would result in traffic routing to both Regions simultaneously. This setup would not meet the requirements for a primary Region failover scenario.