HotKey-Cache: A HotKey-Separate Cache to Improve Performance for Key-Value Store

In most key-value stores, data access patterns are typically non-uniform and display skewness, resulting in the presence of hotkeys and coldkeys. The caching mechanism of key-value stores, which relies on the Least Recently Used (LRU) policy like LRUCache, only accounts for the temporal relevance of the data. In addition, the caching mechanism based on the Least Frequently Used (LFU) policy like LFUCache, only considers the frequency of data access. The limitations of these caching mechanisms lead to a reduction in cache efficiency. This paper presents a novel caching mechanism called HotKey-Cache, which focuses on separating hotkeys. Building upon LRUCache, HotKey-Cache separate hotkeys and assign them to a specialized queue to prevent their direct eviction. This design simultaneously considers both the frequency of data access and the temporal relevance of the data. Finally, we deploy these caches in LevelDB. Experimental results indicated a 12.67% enhancement compared to LRUCache and a 28.52% improvement compared to LFUCache.