Stickiness in Elastic Load Balancing
Amazon have added support for session stickiness in Elastic Load Balancing.
Previously, load balancers routed each request independently to the Amazon EC2 instance with the least load. Now, developers can configure the load balancer so it binds user sessions to specified application instances. All requests made during this session will then be sent to the same application instance.
Please see the Amazon Web Services website for more information.