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MongoDB (from "humongous") is a scalable, high-performance, open source NoSQL database. The database is document-oriented so it manages collections of JSON-like documents. Many applications can thus model data in a more natural way, as data can be nested in complex hierarchies and still be query-able and indexable.

Apache CouchDB is a distributed, fault-tolerant and schema-free document-oriented database accessible via a RESTful HTTP / JSON API. It includes incremental map / reduce mechanics for queries and keeps data safe with an append-only datastore.

RethinkDB pushes JSON to your apps in realtime.

Orchestrate Real Apps on the Cloud with CloudifyAchieve a smooth transition to the cloud and easy automation of even the most complex applications throughout their entire lifecycle with Cloudify. Orchestrate the creation of the whole cloud infrastructure required for your application, starting from compute resources all the way down to networks and block storage devices. Cloudify will then deploy your applications to the cloud (OpenStack, VMWare vSphere, or even bare metal like Softlayer), monitor their progress and scale them when needed. »

Cockroach is a distributed key/value datastore which supports ACID transactional semantics and versioned values as first-class features. The primary design goal is global consistency and survivability, hence the name. Cockroach aims to tolerate disk, machine, rack, and even datacenter failures with minimal latency disruption and no manual intervention. Cockroach nodes are symmetric; a design goal is one binary with minimal configuration and no required auxiliary services.

Couchbase is the NoSQL database market share leader, with production deployments at AOL, Deutsche Post, NTT Docomo, Salesforce.com, Turner Broadcasting Systems, Zynga and hundreds of other organizations worldwide. Couchbase products enable a more flexible, scalable, high-performance, and cost-effective approach to data management than relational database solutions and are particularly well suited for web applications deployed on virtualized or cloud infrastructures, and mobile applications requiring real-time data synchronization between devices and the cloud. Couchbase is a privately held company funded by Accel Partners, Ignition Partners, Mayfield Fund and North Bridge Venture Partners. www.couchbase.com »

Free & open source, high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load.

H2 is a relational database management system written in Java. It can be embedded in Java applications or run in the client-server mode. The disk footprint (size of the jar file) is about 1 MB.

The GridGain In-Memory Data Fabric is a proven software solution, which enables high-performance transactions, real-time streaming and fast analytics in a single, comprehensive data access and processing layer. The In-Memory Data Fabric is designed to easily power both existing and new applications in a distributed, massively parallel architecture on affordable, industry-standard hardware.

Azure DocumentDB is a NoSQL document database service designed from the ground up to natively support JSON and JavaScript directly inside the database engine. It’s the right solution for web and mobile applications when predictable throughput, low latency, and flexible query are key. Microsoft consumer applications like OneNote already use DocumentDB in production to support millions of users.

Titan is a scalable graph database optimized for storing and querying graphs containing hundreds of billions of vertices and edges distributed across a multi-machine cluster. Titan is a transactional database that can support thousands of concurrent users executing complex graph traversals in real time.

Hazelcast is an in-memory Open Source data grid based on Java. By having multiple nodes form a cluster, data is evenly distributed among the nodes. This allows for horizontal scalability both in terms of available storage space and processing power. Backups are also distributed in a similar fashion to other nodes, based on configuration, thereby protecting against single node failure.

Apache Ignite In-Memory Data Fabric is a high-performance, integrated and distributed in-memory platform for computing and transacting on large-scale data sets in real-time, orders of magnitude faster than possible with traditional disk-based or flash technologies.Apache Ignite In-Memory Data Fabric is designed to deliver uncompromised performance for a wide set of in-memory computing use cases from high performance computing, to the industry most advanced data grid, highly available service grid, and streaming. »

Cachelot works within a fixed amount of memory. No garbage collector. Small metadata, near perfect memory utilization (overhead is 5-7% of the total memory).Smooth responsiveness, without any "gaps" for both read and write operations. Most operations have O(1) complexity.Can be used as a library or as a stand-alone memcached server.