How do ELB sticky sessions enhance user experience?

Sticky sessions, also known as session affinity, significantly enhance user experience by ensuring that requests from the same client are consistently routed to the same instance. When a user initiates a session with an application hosted behind an Elastic Load Balancer (ELB), that user's subsequent requests will go to the same backend instance. This continuity is crucial for applications that maintain user state or session data, such as shopping carts or user profiles.

By directing all requests from a particular user to the same instance, the application can leverage already-established session data, reducing the need to recreate or retrieve that state with each new request. This leads to faster response times and a smoother overall experience for the user, as they do not need to re-establish context with each interaction.

Other options, while relevant to various aspects of application performance and security, do not directly pertain to the improvement of the user experience in the context described. For instance, balancing traffic across multiple zones primarily addresses availability and fault tolerance rather than user session management. Similarly, encrypting data in transit and providing automatic SSL certificate management focus on security aspects rather than the continuity of the user experience through session handling.