Ideally, applications run as stateless processes where every use case is executed self-sufficiently, without affecting other running processes. Potential state is either stored in an attached resource such as a database or discarded. Session state that lives longer than a single request is therefore a violation of this principle. The challenge with traditional user session state is that it only resides in a local application instance and not accessible from other instances. The need for so-called sticky sessions on load balancers is an indicator for not having a stateless application.

A lot of modern technology supports this approach. Docker containers with their copy-on-write file system are an example. Stopped containers will be discarded and therefore all of their state is gone as well. Stateless EJBs are based on a similar motivation. However, instances of stateless session beans are pooled and reused, therefore developers need to ensure that no state retains after the business use case invocations.

Enterprise applications should be able to be restarted from scratch without affecting their behavior. This also implies that applications share no state except via well-defined attached resources.