ANS-C01 Question 257
Single answerYour company is hosting a multi-region application on AWS. The application requires low-latency DNS resolution for its clients worldwide. To achieve this, you have set up a Route 53 public hosted zone with a latency-based routing policy and have associated it with EC2 instances running in multiple AWS Regions. However, some users are reporting high latency despite the setup. Upon investigation, you find that their DNS queries are not resolving to the closest region. What could be the cause of this issue?
- A
The Route 53 public hosted zone is not configured with health checks for the EC2 instances.
- B
The DNS resolvers of the clients are not located geographically close to the clients themselves.
- C
The Route 53 latency-based routing policy requires TTL values to be set to zero for optimal performance.
- D
The EC2 instances are not configured with Elastic IP addresses, causing DNS resolution issues.
Show answer and explanation
Correct answer: B
Explanation
Latency-based routing in Route 53 makes routing decisions based on the latency between AWS Regions and the DNS resolver making the request. If a client's DNS resolver is located far from the client (e.g., in another region), the latency-based routing policy may direct traffic to a region closer to the resolver rather than the client. This is a common issue when corporate or ISP DNS resolvers are centralized in a specific location. Understanding how DNS resolvers influence Route 53 routing decisions is critical for diagnosing and resolving these types of latency issues.
- A. Incorrect.
Incorrect: While health checks are important for ensuring that Route 53 only routes traffic to healthy endpoints, the lack of health checks does not cause DNS resolution to bypass the latency-based routing policy.
- B. Correct.
Correct: Latency-based routing in Route 53 relies on the geographic location of the client's DNS resolver, not the client itself. If the resolver is far from the client, it can lead to suboptimal routing.
- C. Incorrect.
Incorrect: TTL values in DNS determine how long a response is cached by a client or resolver but do not directly affect the latency-based routing decision in Route 53.
- D. Incorrect.
Incorrect: Elastic IP addresses are not a requirement for latency-based routing policies in Route 53 and have no impact on the policy's ability to resolve DNS queries based on latency.