1) That all depends on your app, how it is written, what it does, and the types of user and database interactions expected. Using similar hardware and running some standard benchmarking apps we have gotten a few hundred concurrent requests, and thus several thousand simulated active users. 2) What transaction isolation level are you using? From my understanding (I am by no means a Hibernate expert) Hibernate prefers more lenient levels and works best with optimistic locking. (And yes, this is probably a question better asked to the Hibernate community.) 3) What min and max pool sizes did you specify in the *-ds.xml file? The default is 20. 4) There are those that would advocate moving from 5.0.1 to 5.1.0 just to get the bug fixes, but if you have a running system, why switch? (I doubt that the issues you are facing would go away.) 5) Most of you questions are database connection related, so I suspect that a Hibernate book or the Hibernate forum might be a good resource. What database are you using? A presentation on scaling Hibernate application using PostgreSQL was given at the recent JBossWorld. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4255341#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...