You would need to use synchronous replication for such guarantees. A call - e.g., cache.put() - will not return until the same call is successfully executed across the cluster. And if a remote instance is attempting the same thing, it will not complete until the call can be executed across the cluster as well. As such, both calls will block until one of them times out, causing one of the calls to fail and the other to succeed. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4213267#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...