JBoss EAP 6 maintains a number of instances of deployed stateless enterprise beans in memory to provide faster performance. This technique is called bean pooling. When a bean is required the application server can take one from the appropriate pool of already available beans instead of instantiating a new one. When the bean is no longer required it is returned to the pool for reuse.
Bean pools are configured and maintained separately for stateless session beans and for message-driven beans.