CouchDB

vs

ArangoDB

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.

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.

LevelDB is a free and open-source key-value storage library developed by Google. LevelDB provides on-disk storage and ordered mapping of string keys to string values. With LevelDB data is stored and sorted by key, and the keys and values are arbitrary byte arrays. The library will also automatically compress files using the Snappy compression library to optimize for storage capacity.

Redis is a free and open-source, in in-memory data structure store that can be used as a database, cache or message broker. The project is community developed and released under the BSD license. Redis supports common data structures including strings, hashes, lists, sets, sorted sets with range queries, bitmaps, hyperloglogs, geospatial indexes with radius queries and streams.

The worlds most popular free open-source relational database, MySQL is used by 150,000 + companies across the globe. The relational database management system is released and distributed under the GPL license and openly developed by the community. MySQL uses SQL as its query language and is fully integrated and ACID compliant.

PostgreSQL, or Postgres for short is a widely popular, free and open-source relational database management system. PostgreSQL is available for all major operating systems including macOS, Linux, Windows, BSD and Solaris. The project has been in active development for over 30 years now, and powers many of the applications you use on a daily basis.