IBM DB2

vs

CouchDB

RethinkDB is a scalable, open-source database designed for real-time applications. When your app polls your database for data, it becomes slow, unscalable, and cumbersome to maintain. RethinkDB solves this by providing a new database access model, where developers can instruct the database to continuously push updated query results to their applications, without polling.

BigchainDB allows developers and enterprise to deploy blockchain proof-of-concepts, platforms and applications with a blockchain database, supporting a wide range of industries and use cases. BigchainDB provides high throughput, low latency, powerful query functionality, decentralized control, immutable data storage and built-in asset support, BigchainDB is like a database with blockchain characteristics.

NuoDB is a distributed relational database management system utilizing SQL. The database is architected to meet the rapidly evolving demands of today's enterprises, NuoDB can be used to deploy on-premise, extend to the cloud, scale on demand, eliminate downtime and reduce total cost of ownership. All while maintaining SQL compatibility and a workflow that most developers are familiar with.

MongoDB is an open-source document-oriented distributed database built for modern applications. MongoDB uses JSON-like documents with optional schemas and is classified as a NoSQL database. The database is freely distributed under the Server Side Public License, but MongoDB provides commercial version of the database for enterprise-scale applications.

ArangoDB is a database system that was designed to support key/value, document, and graph data to be stored together, and queried via a unified language called AQL. The project is developed by ArangoDB GmbH, and released free and open-source under the Apache License 2.0. The universal "native multi-level" design of the database allows for a flexible approach when structuring and building an application, a feature that many have come to love.

OrientDB is an open-source NoSQL database management system written in Java. The multi-model database supports graph, document, key/value, and object models, where relationships are managed as in graph databases with direct connections between records. The database is extremly efficient and can store over 220,000 records per second on common hardware, and traverse thousands of records in milisecons. OrientDB scales well on multiple machines, thanks to the multi-master replication where there is no single bottleneck on writes like with master-slave replication.