A. Use an Amazon Route 53 multivalue answer routing policy to route older client traffic to the on-premises application version and the rest of the traffic to the new AWS based version.
B. Use a Classic Load Balancer for the new application. Route all traffic to the new application by using an Elastic Load Balancing (ELB) load balancer DNS. Define a user-agent-based rule on the backend servers to redirect earlier clients to the on-premises application.
C. Use an Application Load Balancer for the new application. Register both the new and earlier applications as separate target groups and use path-based routing to route traffic based on the application version.
D. Use an Application Load Balancer for the new application. Register both the new and earlier application backends as separate target groups. Use host header- based routing to route traffic based on the application version.