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Difficulty: MediumRoute 53 Routing Policies and DNS Failover Strategies

A global e-learning company serves dynamic content to users worldwide. The application backend is deployed behind Application Load Balancers (ALBs) in both the eu-central-1 and ap-southeast-1 regions. The company wants to route users to the region that provides the lowest network latency. If one of the regions experiences an outage, Route 53 must automatically stop routing traffic to that region's ALB. The application uses the apex domain learn.example.com. Which configuration should the solutions architect implement to meet these requirements?

  1. A
    Create Latency Alias records for the apex domain pointing to the ALBs in each region, and set the 'Evaluate Target Health' parameter to 'No' to maximize DNS caching efficiency.
  2. B
    Create Latency Alias records for the apex domain. Configure the primary record to point to the eu-central-1 ALB, and configure the secondary record to point directly to the DNS endpoint of the Amazon RDS read replica in ap-southeast-1.
  3. Create Latency Alias records for the apex domain pointing to the respective ALBs in each region, and set the 'Evaluate Target Health' parameter to 'Yes' on both records.Answer
  4. D
    Create Failover records for the apex domain, pointing the primary record to the eu-central-1 ALB. Point the secondary record to a stopped EC2 instance in ap-southeast-1 that serves as a standby database, expecting Route 53 to automatically start the instance and route traffic during a failover.

Answer

Create Latency Alias records for the apex domain pointing to the respective ALBs in each region, and set the 'Evaluate Target Health' parameter to 'Yes' on both records.
The correct configuration utilizes Latency-based routing with Alias records pointing to the ALBs in each region. Because the zone apex domain (learn.example.com) is used, CNAME records are not permitted, necessitating Alias records. Setting 'Evaluate Target Health' to 'Yes' allows Route 53 to determine the health of the ALBs based on the underlying target group health checks, enabling automatic failover and routing redirection during a regional outage.

Step-by-Step Solution

1
Determine the routing policy and record type required for the zone apex domain.
An Alias record must be used because DNS standards do not allow CNAME records at the zone apex (learn.example.com). To satisfy the requirement of routing to the lowest latency region, Latency-based routing must be used.
Alias records allow mapping the zone apex to AWS resources like ALBs, and Latency routing satisfies the performance requirement.
2
Configure health checks and automatic failover mechanism.
Enable the 'Evaluate Target Health' setting (set to Yes) on the Route 53 Latency Alias records pointing to the ALBs.
This allows Route 53 to inherit the health of the ALB (based on its target group health checks) to stop routing traffic to an unhealthy region automatically without needing a separate Route 53 health check.

Key Concept

Route 53 Latency Routing with Alias records and Target Health Evaluation
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Topics

Route 53 Routing Policies and DNS Failover Strategies

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