AWS Certified Solutions Architect Associate Test 10

An Elastic Load Balancer(ELB) by default, routes each request independently to the applicationinstance with the smallest load. However, you can use the sticky session feature (also known assession affinity), which enables the load balancer to bind a user's session to a specific applicationinstance. This ensures that all requests coming from the user during the session will be sent to thesame application instance. The key to managing the sticky session is determining how long your loadbalancer should consistently route the user's request to the same application instance. If yourapplication has its own session cookie, then you can set Elastic Load Balancing to create the sessioncookie to follow the duration specified by the application's session cookie. If your application doesnot have its own session cookie, then you can set Elastic Load Balancing to create a session cookie byspecifying your own stickiness duration. You can associate stickiness duration for only HTTP/HTTPSload balancer listeners. An application instance must always receive and send two cookies: A cookiethat defines the stickiness duration and a special Elastic Load Balancing cookie named AWSELB, thathas the mapping to the application instance.
Reference:
http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/TerminologyandKeyConcepts.html#session-stickiness