Gizzard

".. Gizzard is a middleware networking service that manages partitioning data across arbitrary backend datastores (e.g., SQL databases, Lucene, etc.). The partitioning rules are stored in a forwarding table that maps key ranges to partitions. Each partition manages its own replication through a declarative replication tree. Gizzard supports migrations (for example, elastically adding machines to the cluster) and gracefully handles failures. The system is made eventually consistent by requiring that all write-operations are idempotent AND commutative and as operations fail (because of, e.g., a network partition) they are retried at a later time." ..

.. built on/with Scala and Thrift ..