Currently Crowd login session tokens are stored in the primary DB (in our case postgres). However the usage patterns of the updates and deletes on these do not suit an ACID database, and frequent reindexes are required to stop perfomance degradation. Over time this can cause long delays during authentication. More information here. As this is volatile data it would be better stored in a Crowd-local cache, preferably disk-backed. This would improve overall performance both for authentication and for other DB apps.