Spring Security ACL is, by its current implementation, based on SQL databases which joins together all 4 tables (sid, class, object_identity & access_control_entry) on lookup time. Some projects (1,2,3) added support for MongoDB to avoid having to join these 4 tables on every lookup (if no cache hit was found) and utilize the flexibility of embedded documents.

A similar question was also raised on StackOverflow asking if there is a performance reason to support only SQL based databases but not NoSQL ones.

As I have also implemented a MongoDB based ACL Spring Security Service (3), I wanted to ask if there is generel interest to include this (or any of the other projects) into the Spring Security codebase. I am aware that some modifications to the code (to adhere to the general guidelines) has yet to be done, but before putting in more work I just wanted to make sure if there is general interest otherwise my time is probably better spent elsewhere :)

I've also ported the contact ACL sample (4) to use my MongoDB ACL implementation (3) in order to showcase its functionality on an existing sample that made use of ACL.

1 Implementation by Peter Arsentev
2 Implementation by Alex Czar (though forked from somewhere else I guess)
3 Implementation by Roman Vottner
4 Contact ACL Sample port to MongoDB ACL