An interesting read, showing that Hibernate can quickly get to its limits when it comes to querying 50k records – a relatively small number of records for a sophisticated database:
http://koenserneels.blogspot.ch/2013/03/bulk-fetching-with-hibernate.html
Of course, Hibernate can generally deal with such situations, but you have to start tuning Hibernate, digging into its more advanced features. Makes one think whether second-level caching, flushing, evicting, and all that stuff should really be the default behaviour…?