Hello caching experts! At last minute before Hibernate ORM 5, I'm proposing a change in the second level caching SPI. I've already implemented it, including patching both the Ehcache and Infinispan modules to satisfy the new requirement, so you don't have to do much but please have a look and hopefully approve: - https://github.com/hibernate/hibernate-orm/pull/974 The summary is: - The CacheKey SPI is changed to an interface - I'm adding a factory method to each Region to allow the cache implementor to produce its own key implementations - Patched all current Region implementations to simply produce the old, proven key implementation. - Changed all code in ORM which deals with cache access to exclusively use the new factory. - All signatures using a "key" have been changed from Object to the respective contract Since Hibernate ORM 5 is almost ready I'm only defining the API changes; the description on the PR should give some possible suggestions of optimisations which we could then play with. As a background: we had several tests showing that the allocation cost of the CacheKey implementation being "imposed" by the Hibernate core was quite high; this is a first step to improve that, to allow slimming of these but also possible further crazy ideas such as HHH-9780. Thanks, Sanne