For Hibernate Search, I did introduce the IndexReaders caching. My tests shows for: - a search intensive application, - low update ratio - in-memory database - filesystem based index a speed increase of 25 to 30%. It is not the default yet (use 'hibernate.search.reader.strategy shared' to enable), but once it's tested, it will be. It was not a piece of cake (to say the least), I would appreciate a couple of pairs of eyes on the code, as it involves locking and JMM understanding. I think I reduced the lock windows as much as possible but if someone's got ideas (or think it's unsafe), fell free to share. The code is here http://fisheye.jboss.org/browse/Hibernate/trunk/HibernateExt/search/ src/java/org/hibernate/search/reader/SharedReaderProvider.java?r=11576