You are having trouble maintaining session states on some of your applications using an Elastic Load Balancer(ELB). Requests from the same session should be routed to the same target in the target group. Which of the following is the quickest and cost-efficient method to implement this?

Answer options:

A.Disable Sticky session. Use Elasticache to put session data. Elasticache is easy to set up, manage, and scale a distributed in-memory cache environment in the cloud.
B.Use a special cookie to track the instance for each request to each listener. When the load balancer receives a request, it will then check to see if this cookie is present in the request.
C.Use the sticky session feature (also known as session affinity), enabling the load balancer to bind a user`s session to a specific instance. This ensures that all requests from the user during the session are sent to the same instance.
D.If your application does not have its own session cookie, then you can configure Elastic Load Balancing to create a session cookie by specifying your own stickiness duration.

Answer – C
Option A is incorrect because although ElastiCache can be utilized to store the session state in the cache rather than in any database, it is slow to implement and not cost-efficient if compared with option
C.Option C is CORRECT because Sticky sessions, also known as session affinity, allow you to route a site user to the particular web server managing that individual user’s session. It is also the most cost-efficient method.
Options B and D are incorrect because they describe the methods partially and do not clearly indicate that the sticky session feature should be used.
Reference can be found in https://aws.amazon.com/caching/session-management/.