SAP-C02 Practice Question 89: Weighted DNS Phased Cutover

AWS Certified Solutions Architect – Professional (SAP-C02) · Test 9 · question 9 of 10

Migration and Modernizationmedium

A company is moving a customer-facing web application from its data center to AWS. It wants to shift traffic in stages, for example 5 percent, then 25 percent, then 100 percent, watching error rates between stages, and to be able to send all traffic back to the data center immediately if problems appear. The application is reached at www.example.com, and the on-premises endpoint and the new Application Load Balancer are both healthy. The team has lowered the DNS TTL in advance.

Which solution meets these requirements?

Show answer and explanation

Answer:

A. Create Route 53 weighted records for the on-premises endpoint and the load balancer, and change their weights at each stage

With weighted routing, *"you can link multiple resources to a single domain name ... and choose how much traffic goes to each resource."* Route 53 sends traffic based on the weight of a record *"as a share of the total weight for all records in the group,"* and AWS notes it is useful for *"testing new versions of software."* You can *"slowly change the balance by changing the weights"*, and *"if you want to stop sending traffic to a resource, change the weight for that record to 0"*, which is the rollback (option A). The lowered TTL makes each change take effect quickly.

- B is wrong because failover routing sends all traffic to the primary and switches only when its health check fails. It cannot send 5 or 25 percent to the new endpoint. - C is wrong because latency-based routing sends each user to the endpoint with the lowest latency, not a share that the team controls. - D is wrong because geolocation routing splits traffic by the user's location, so the stages would be decided by geography, not by a percentage.

Reference: Weighted routing

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