Forward Thinking

• Proven
  Cassandra is in use at Netflix, Twitter, Urban Airship, Constant Contact, Reddit, Cisco, OpenX, Digg, CloudKick, Ooyala, and more companies that have large, active data sets. The largest known Cassandra cluster has over 300 TB of data in over 400 machines.
• Fault Tolerant
  Data is automatically replicated to multiple nodes for fault-tolerance. Replication across multiple data centers is supported. Failed nodes can be replaced with no downtime.
• Decentralized
  There are no single points of failure. There are no network bottlenecks. Every node in the cluster is identical.
• You’re in Control
  Choose between synchronous or asynchronous replication for each update. Highly available asynchronus operations are optimized with features like Hinted Handoffand Read Repair.
• Rich Data Mode
  Allows efficient use for many applications beyond simple key/value.
• Elastic
  Read and write throughput both increase linearly as new machines are added, with no downtime or interruption to applications.
• Durable
  Cassandra is suitable for applications that can’t afford to lose data, even when an entire data center goes down.
• Professionally Supported
  Cassandra support contracts and services are available from third parties.

http://cassandra.apache.org/

An Amazon AWS SimpleDB library for Node.js that is user-friendly and fault-tolerant.

https://github.com/rjrodger/simpledb

node-mdb is a Node.js-based Open Source clone of Amazon SimpleDB. It is a re-implementation of M/DB, but re-written in Node.js Javascript. Like M/DB, it uses the free, Open Source GT.M database as the data repository.node-mdb is a fully-fledged database, not simply a mock service.

https://github.com/robtweed/node-mdb

Globals is a Fast, Proven, Simple, Flexible, NoSQL Database from InterSystems that is FREE for everyone. At its core, the Globals database is powered by an extremely efficient multidimensional data engine. The exposed interface supports access to the multidimensional structures – providing the highest performance and greatest range of storage possibilities.

http://globalsdb.org/

Persistence is a project to allow a high level API for persisting data between process runs. The goal is to support backends that are easy to use, powerful, flexible, or all of the above if possible.

https://github.com/creationix/node-persistence

Riak is a Dynamo-inspired database that is being used in production by companies like Mozilla and Comcast. Riak scales predictably and easily and simplifies development by giving users the ability to quickly prototype, test, and deploy their applications.

http://wiki.basho.com/Riak.html

http://www.barricane.com/barricane-db/

Redis is an open source, advanced key-value store. It is often referred to as a data structure server since keys can contain strings, hashes, lists, sets and sorted sets.
You can run atomic operations on these types, like appending to a string; incrementing the value in a hash; pushing to a list; computing set intersection, union and difference; or getting the member with highest ranking in a sorted set.
In order to achieve its outstanding performance, Redis works with an in-memory dataset. Depending on your use case, you can persist it either by dumping the dataset to disk every once in a while, or by appending each command to a log.
Redis also supports trivial-to-setup master-slave replication, with very fast non-blocking first synchronization, auto-reconnection on net split and so forth.
Other features include a simple check-and-set mechanism, pub/sub and configuration settings to make Redis behave like a cache.
You can use Redis from most programming languages out there.
Redis is written in ANSI C and works in most POSIX systems like Linux, *BSD, OS X and Solaris without external dependencies. There is no official support for Windows builds, although you may have some options.

Redis is sponsored by VMWare and is at the time of writing one of the most popular alternatives available.

http://redis.io/

MongoDB (from “humongous”) is a scalable, high-performance, open source, document-oriented database. Written in C++

http://www.mongodb.org/