Works the same as the basic memoization function (i.e. `memo` and `core.memoize` except when a given threshold is breached. Observe the following: (require '[clojure.core.memoize :as memo]) (def id (memo/lru identity :lru/threshold 2)) (id 42) (id 43) (snapshot id) ;=> {[42] 42, [43] 43} At this point the cache has not yet crossed the set threshold of `2`, but if you execute yet another call the story will change: (id 44) (snapshot id) ;=> {[44] 44, [43] 43} At this point the operation of the LRU cache looks exactly the same at the FIFO cache. However, the difference becomes apparent on further use: (id 43) (id 0) (snapshot id) ;=> {[0] 0, [43] 43} As you see, once again calling `id` with the argument `43` will expose the LRU nature of the underlying cache. That is, when the threshold is passed, the cache will expel the **L**east **R**ecently **U**sed element in favor of the new.