Question 18
Domain 3: Resilient Cloud SolutionsA DevOps team operates an integration service that runs on an Amazon EC2 instance. The DevOps team uses Amazon Route 53 to manage the integration service's domain name by using a simple routing record. The integration service is stateful and uses Amazon Elastic File System (Amazon EFS) for data storage and state storage. The integration service does not support load balancing between multiple nodes. The DevOps team deploys the integration service on a new EC2 instance as a warm standby to reduce the mean time to recovery. The DevOps team wants the integration service to automatically fail over to the standby EC2 instance. Which solution will meet these requirements?
Correct answer: A
Explanation
Route 53 weighted routing lets you send all traffic to one endpoint by setting its weight to 100 and keep a standby endpoint at 0, then shift traffic automatically when health checks fail. The setup matches the need for a warm standby because the service "does not support load balancing between multiple nodes" and the records can fail over using "an application health check with each record."
Why each option is right or wrong
A. Update the existing Route 53 DNS record's routing policy to weighted. Set the existing DNS record's weighting to 100. For the same domain, add a new DNS record that points to the standby EC2 instance. Set the new DNS record's weighting to 0. Associate an application health check with each record.
Route 53 weighted routing is the only policy here that can keep one EC2 endpoint active while holding a second, warm-standby endpoint in reserve for the same name; with weights of 100 and 0, all DNS answers go to the primary until health evaluation changes. Under Route 53 health-check behavior, if the primary record fails its associated application health check, Route 53 stops returning that record and can answer with the standby record instead, which fits a stateful service that cannot be load balanced across multiple nodes.
B. Update the existing Route 53 DNS record's routing policy to weighted. Set the existing DNS record's weighting to 99. For the same domain, add a new DNS record that points to the standby EC2 instance. Set the new DNS record's weighting to 1. Associate an application health check with each record.
A 99/1 split still sends some live traffic to standby, which is not true standby behavior.
C. Create an Application Load Balancer (ALB). Update the existing Route 53 record to point to the ALB. Create a target group for each EC2 instance. Configure an application health check on each target group. Associate both target groups with the same ALB listener. Set the primary target group's weighting to 100. Set the standby target group's weighting to 0.
An ALB distributes requests across targets; this service explicitly does not support load balancing between nodes.
D. Create an Application Load Balancer (ALB). Update the existing Route 53 record to point to the ALB. Create a target group for each EC2 instance. Configure an application health check on each target group. Associate both target groups with the same ALB listener. Set the primary target group's weighting to 99. Set the standby target group's weighting to 1.
A 99/1 ALB weighting sends traffic to both instances and violates the no-load-balancing constraint.