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Difficulty: MediumRoute 53 Routing Policies and DNS Failover Strategies

A company operates a global shipment tracking API at api.shipments.example.com. The application is deployed in the eu-central-1 and ap-southeast-1 Regions behind an Application Load Balancer (ALB) in each Region. The company wants an active-active setup that routes users to the Region with the lowest network latency. If an ALB in one Region fails, Route 53 must automatically stop routing traffic to that Region. Which configuration meets these requirements with the lowest administrative complexity and cost?

  1. A
    Create Route 53 Latency CNAME records for api.shipments.example.com pointing to the ALB DNS names, and set Evaluate Target Health to Yes.
  2. B
    Create Route 53 Failover Alias records pointing to the ALBs, configuring eu-central-1 as primary and ap-southeast-1 as a pilot light secondary that only provisions compute resources after a failover event is detected.
  3. Create Route 53 Latency Alias records for api.shipments.example.com pointing to the Application Load Balancer (ALB) in each Region, and set Evaluate Target Health to Yes.Answer
  4. D
    Create Route 53 Latency Alias records pointing to the ALBs, and configure the DNS failover to route traffic directly to the Amazon RDS Read Replica in the secondary Region when the primary database becomes unhealthy.

Answer

Create Route 53 Latency Alias records for api.shipments.example.com pointing to the Application Load Balancer (ALB) in each Region, and set Evaluate Target Health to Yes.
The correct configuration uses Route 53 Latency Alias records pointing to the Application Load Balancers with Evaluate Target Health set to Yes. This fulfills the active-active requirement by routing users to the Region with the lowest latency, and it automatically stops routing traffic to a Region if its ALB becomes unhealthy, using the inherited ALB health checks without any extra cost or administrative overhead.

Step-by-Step Solution

1
Analyze the active-active and latency requirements.
Determine that Latency routing must be used to send clients to the closest Region to minimize latency, rather than Failover routing which is active-passive.
The requirement specifies routing users to the Region with the lowest network latency under normal operating conditions.
2
Determine the health checking and failover mechanism.
Identify that 'Evaluate Target Health' must be set to Yes to let Route 53 monitor the ALBs automatically.
Enabling Evaluate Target Health allows Route 53 to check the health of the ALB targets and stop routing traffic if they fail, without needing custom HTTP health checks.
3
Evaluate record types (Alias vs CNAME) for the load balancers.
Select Alias records because Route 53 'Evaluate Target Health' is only supported on Alias records, and Alias records do not incur DNS query charges.
CNAME records do not support the 'Evaluate Target Health' feature directly, requiring additional configurations and costs.

Key Concept

Route 53 Latency Alias routing with Evaluate Target Health enables cost-effective, low-latency, active-active regional failover.
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Topics

Route 53 Routing Policies and DNS Failover Strategies

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