membase - distributed key-value database
Membase is an distributed, key-value database management system optimized for storing data behind interactive web applications. These applications must service many concurrent users, creating, storing, retrieving, aggregating, manipulating and presenting data in real-time. Supporting these requirements, membase processes data operations with quasi-deterministic low latency and high sustained throughput.
For those familiar with memcached, membase provides on-the-wire protocol compatibility, but adds disk persistence; hierarchical storage management; data replication; live cluster reconfiguration and rebalancing; and secure multi-tenancy with data partitioning.
Membase scales elastically, with linear cost. Servers can be added to, or removed from, a running cluster with no application downtime.