1. A method comprising: generating a plurality of session objects at an application server in response to client requests, the session objects storing session data defining a state of interaction with each of a respective plurality of clients; defining a hierarchy of session object storage units at the application server, the session object storage units to store session objects having one or more related session management criteria, the session management criteria comprising at least one of a maximum inactive time interval, a maximum number of outstanding requests or a multithreading policy; grouping the session objects, at the application server, within the session object storage units based on the one or more related session management criteria of each of the session objects; generating a persistent representation of the hierarchy of session object storage units at the application server, the persistent representation of the session object storage units mapping each session storage object unit and each individual session object within each session object storage unit to different persistent data structures within a persistent storage device, generating the persistent representation includes mapping each session object storage unit to a first hierarchical level and mapping each session object stored within the session object storage units to a second hierarchical level, the second hierarchical level positioned under the first hierarchical level.