A highly scalable parallel caching system for web search engine results

This paper discusses the design and implementation of SDC, a new caching strategy aimed to e ciently exploit the locality present in the stream of queries submitted to a Web Search Engine. SDC stores the results of the most frequently submitted queries in a fixed-size read-only portion of the cache, while the queries that cannot be satis ed by the static portion compete for the remaining entries of the cache according to a given cache replacement policy. We experimentally demonstrated the superiority of SDC over purely static and dynamic policies by measuring the hit-ratio achieved on two large query logs by varying cache parameters and the replacement policy used. Finally, we propose an implementation optimized for concurrent accesses, and we accurately evaluate its scalability.