Sakai's default cache sizes and expiration settings are conservative and most likely need to be adjusted at large institutions.
On a running production instance, you can find maxed out caches by logging in as an admin user, going to Administration Workspace -> Memory - Status and looking for maxed-out caches. A maxed-out cache will have a count value of 10000 or 100000.
All caches should be adjustable in Sakai 10.0+ with a simple modification to sakai.properties.
Adjust the caching of users especially if you use the JLDAP provider. This example will cache up to 50k users for up to half a day each:
Adjust the realm/role group cache to retain items in the cache for two hours:
The user/site cache keeps track of the sites associated with the user:
The security service cache retains information about permission requests (e.g., can user xxxx do asn.submit in /site/abc):