Arcus is a memcached-based cache cloud developed by NAVER Corp. Memcached has been heavily modified to support functional and performance requirements of NAVER services. Arcus is normally positioned in front of a back-end storage, such as DB, where it stores/retrieves hot-spot data of service applications using fast main memory. Therefore, Arcus provides very fast data access for service applications and reduces the load on back-end storage. In addition, Arcus can serve as a fast shared storage. Remote service processes usually store complex query results, computation-intensive results, and intermediate results of web processing in Arcus cache cloud so any process can access them.Arcus provides two new significant features over the existing memcached.