...
Assumptions
Various implementations of 'provided' information to realms impose a wide variety of costs for getting the latest information about realm memberhips.
Dirty Cache Problem
I is useful to look at this issue as having similar characteristics as any typical cache implelentation might have. The purpose of a cache is to reduce average access time for data. And there are many ways to approach the codification of a cost/benefit analysis for deciding when to use a cached value for any given environment.
In this case, the cached data is the realm information stored in the internal Sakai database tables relating to authzGroups. The cache is determined to be 'dirty' (needs to be updated with the latest data) if