The document discusses and compares caching technologies for Java applications, specifically Memcached and DistributedMap. It provides an overview of general object cache characteristics and how cache instances work. Memcached is described as an open-source, high-performance distributed memory caching system where each cluster of servers is a single cache instance. DistributedMap is a built-in component of WebSphere Application Server that allows for multiple cache instances within a single JVM. The document outlines some advantages of each system and poses some open questions for further performance comparisons.

3. Memcached

4. DistributedMap (part of Dynacache)

8. Identical keys in two separate cache instances do not collide

9. Cache statistics can typically be monitored on an instance level

10. Support for creating multiple instances varies by cache implementation

15. Each key is cached on at most one server

16. Explicit invalidations go only to the server which should store that key

18. Explicit invalidation notifies peers to discard the cache key

19. Option available to push entries to peers on cache insert

23. Priority-based LRU algorithm