Galaxy: Can fit into an in-memory grid
Galaxy[http://puniverse.github.com/galaxy/]
Galaxy is a high-performance in-memory data-grid (IMDG) that can serve as a basis for building distributed applications that require fine-tuned control over data placement and/or custom distributed data-structures.
What makes Galaxy different from other IMDGs is the way it assigns data items to cluster node. Instead of sharding the data on one of the keys using a consistent hashing scheme, Galaxy dynamically moves objects from one node to another as needed using a cache-coherence protocol similar to that found in CPUs. This makes Galaxy suitable for applications with predictable data access patterns, i.e. applications where the data items behave according to some proximity metric, and items that are “closer” together are more likely to be accessed together than items that are “far” apart.
Galaxy is not a key-value store, though it can be used to build one. It’s meant to be used as a low-level platform for building distributed data structures.
Galaxy uses ZooKeeper or JGroups for cluster management, and BerkeleyDB or any SQL database for optional persistence.