A customer had a problem whereby JIRA was "freezing" often. The culprit was that the CachingVersionStore was locking people out while it populated its cache.

The admins where changing the order of a version for a single project but ALL versions for all projects where being discarded from the cache and re fetched.

(The low level problem was the the DB update was slow as well but this just made it worse. And to make matters even worse the "re-order" versions was being do on the UI and hence the cache was
locked and re-populated multiple times in a short space of tuime.)

The CachingVersionStore could use a different locking, such as perhaps lock "striping" to based on say project key so that only parts of the Cache would be unavailable at a time and hence users need not be locked out from Issue interactions for long periods.

Of course this would only benefit people with heavy load and frequently changing project versions (and perhaps slow databases).