AWS Certified Advanced Networking – Specialty (ANS-C01) — Question 136

A company is deploying a web application into two AWS Regions. The company has one VPC in each Region. Each VPC has three Amazon EC2 instances as web servers behind an Application Load Balancer (ALB). The company already has configured an Amazon Route 53 public hosted zone for example.com. Users will access the application by using the fully qualified domain name (FQDN) of app.example.com.

The company needs a DNS solution that allows global users to access the application. The solution must route the users' requests to the Region that provides the lowest response time. The solution must fail over to the Region that provides the next-lowest response time if the application is unavailable in the initially intended Region.

Which solution will meet these requirements?

Answer options

• A. For each ALB, create an A record that has a geolocation routing policy to route app.example.com to the IP addresses of the ALB. Configure a Route 53 HTTP health check that monitors each ALB by IP address. Associate the health check with the A records.
• B. Create an A record that has a geolocation routing policy to route app.example.com to the IP addresses for both ALBs. Configure a Route 53 health check that monitors TCP port 80 for each ALB by IP address. Associate the health check with the A records.
• C. Create an A record that has a latency-based routing policy to route app.example.com as an alias to one of the ALBs. Configure a Route 53 health check that monitors TCP port 80 for each ALB by IP address. Associate the health check with the A records.
• D. For each ALB, create an A record that has a latency-based routing policy to route app.example.com as an alias to the ALB. Set the value for Evaluate Target Health to Yes for the records.

Correct answer: D

Explanation

The correct answer is D, which utilizes a latency-based routing policy that directs traffic to the ALB with the lowest response time and incorporates health checks to ensure availability. This approach ensures that if one ALB becomes unavailable, traffic will automatically reroute to the next available ALB. The other options either use geolocation routing or do not effectively utilize latency-based routing with health checks, which do not meet the requirement for optimal response times and failover capabilities.