You are working as a SysOps administrator for a large multinational organization. They have a set of critical web servers spread across the globe. For Web servers in us-east-1 region & us-west-1 region, you have configured latency-based routing followed by weighted routing policy between web servers in different AZ. These Web servers are behind ELB. Alias records are created using Route 53 pointing web server domain to this ELB. During failover testing you are observing that traffic is not shifting to us-west-1 post all instance down in us-east-1 region.What might be a possible reason for this?

Answer options:

A.Health Checks for ELB in the US-east-1 region is missing.
B.Routing Policy is misconfigured. Failover routing should be used instead of a weighted routing policy.
C.Evaluate Target Health check is missing in Alias records for ELB in US-east-1 region.
D.Route 53 Health check is missing for US-east-1region.

Correct Answer: C
In case of complex routing policy for Route 53, a health check for all records alias & non-alias is necessary. Route 53 will assume it’s working & traffic is not diverted to healthy instance for missing health check. In the above case, health check evaluation should be enabled for alias records in us-east 1. When all instances in this region are down, traffic will be shifted to servers in us-west-1.
Option A is incorrect as If a Health check is being configured on Route 53, additional health checks on ELB are not required.
Option B is incorrect as in this case, latency routing is used to shift traffic between 2 regions & weighted routed policy between instances in different AZ of each region. With health checks missing, a failover policy will not be useful in this case.
Option D is incorrect as Route 53 is a global service, no need to specify Region while creating a Health check.
 For more information on health checks for complex routing, refer to the following URL-
https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/dns-failover-complex-configs.html