Stickiness is a term that is used to describe the functionality of a load balancer to repeatedly route traffic from a client to a single destination, instead of balancing the traffic across multiple destinations. For example, traffic from client A can be continually routed to a specific server, so that server can maintain session state data. If traffic from client A is routed to two distinct servers, each server might be missing important information that’s available to the other server.
https://docs.aws.amazon.com/prescriptive-guidance/latest/load-balancer-stickiness/welcome.html