OrientDB is a NoSQL DBMS which can store 150,000 documents per second on common hardware. Even with a document-based database, the relationships are managed as in graph databases, with direct connections among records. You can traverse entire or parts of trees and graphs of records in a few milliseconds. It supports schema-less, schema-full, and schema-mixed modes, has a strong security profiling system based on users and roles, and supports SQL between the query languages. Thanks to the SQL layer, it's straightforward to use for people skilled in the relational world.
Membase is a distributed key-value database management system, optimized for storing data behind interactive Web applications. Membase automatically spreads data and I/O across servers. This "scale out" approach at the data layer permits virtually unlimited growth of transaction capacity, with linear increases in cost and constant per-operation performance. Membase is in production behind thousands of applications, from shared-server deployments at Heroku to dedicated Membase clusters with hundreds of servers at Zynga and NHN.
VoltDB is a blazingly fast relational database system. It is specifically designed to run on modern scale-out architectures: fast, inexpensive servers connected via high-speed data networks. It is aimed at a new generation of database applications - real-time feeds, sensor-driven data streams, micro-transactions, low-latency trading systems - requiring database throughput that can reach millions of operations per second. What’s more, the applications that use this data must scale on demand, provide flawless fault tolerance, and enable real-time visibility into the data that drives business value. It includes client application drivers for applications written in Java, C++, C#, PHP, and Python. VoltDB community members have also authored client libraries for Erlang, Ruby and Node.js. There are streaming export capabilities for leading analytic database environments, including Apache Hadoop.
EJDB is an embedded JSON database engine. It aims to be a fast MongoDB-like NoSQL library that can be embedded into C/C++/Nodejs/Python3/Lua applications. It features collection-level write locking, collection level transactions, string token matching queries, and a Node.js binding.
UnQLite is a in-process software library which implements a self-contained, serverless, zero-configuration, transactional NoSQL database engine.It is a document store database similar to MongoDB, Redis, CouchDB, etc. as well a standard key/value store similar to BerkeleyDB, LevelDB, etc. It reads and writes directly to ordinary disk files. A complete database with multiple collections is contained in a single disk file. The database file format is cross-platform, and you can freely copy a database between 32-bit and 64-bit systems or between big-endian and little-endian architectures.