When using server farms and load balancers to deliver web applications to end users, it is often necessary to ensure that some user sessions are created on the same backend server after a previous session has ended. This is typically the case when a user was in the middle of a task that they need to come back and complete, or if they were on a commerce site and you wanted them to return to an instance of a web application that includes any items they have placed in a shopping cart.
This behavior on web server farms is known as persistence, session persistence, or as sticky sessions. Session persistence is a feature of a load balancer such as the Kemp LoadMaster. It stores the information needed to ensure that broken sessions and returning clients are connected to the correct backend server instance so they can continue their previous session.