1  In memory Key/Value store with LRU expire and concurrent access
 2  
 3  
 4  # Description
 5  
 6  Items are stored in N sharded/bucketized HashMaps to improve concurrency.  Every Item is
 7  always behind a RwLock.  Quering an item will return a guard associated to this lock.
 8  Items that are not locked are kept in a list to implement a least-recent-used expire
 9  policy.  Locked items are removed from that lru list and put into the lru-list when they
10  become unlocked.  Locked Items will not block the hosting HashMap.
11