Persistence and Stickiness for SA dictionary:
When customers visit an e-commerce site, they usually start by browsing the site. Depending on the application, the site may require that the client become persisted (stuck) to one server as soon as the initial connection is established, or the application may require this action only when the client starts to create a transaction, such as when building a shopping cart.
For example, after the client adds items to a shopping cart, it is important that all subsequent client requests are directed to the same real server so that all the items are contained in one shopping cart on one server. An instance of a customer’s shopping cart is typically local to a particular server rather than duplicated across multiple servers.
E-commerce applications are not the only types of applications that require a sequence of client requests to be directed to the same real server. Any web applications that maintain client information may require stickiness, such as banking and online trading applications, or FTP and HTTP file transfers.
More info: Cookies, Sessions, and Persistence