An Acronym for Least Frequently Used.
This is a Cache entry expiry strategy. On cache miss, the least frequently used record is discarded from cache to be replaced by the data read for the request which caused the cache miss.
While this approach leads to very efficient utilization of the Cache's capacity, it requires complex bookkeeping. The overhead incurred is rarely worth the effort and only pays off if a cache miss is many orders of magnitude more expensive than a cache hit. Even HardDisk Caches, where the disparity between hit and miss is a factor of about 1,000, LFU may not achieve significantly better performance than LRU.