Redis is the world's most popular in-memory database and cache system, developed by Redis Ltd. (formerly Redis Labs), offering open-source Redis Stack, Redis Enterprise, and Redis Cloud services.
Neo4j is the world's leading graph database company, founded in 2007 by Emil Eifrem and others, headquartered in San Mateo, California, USA, offering a native graph database, the Cypher query language, and GraphRAG AI capabilities widely used in fraud detection and knowledge graphs.
Apache CouchDB is an open-source document database maintained by the Apache Software Foundation, storing data in JSON with a pure HTTP/JSON API, known for multi-master replication and offline-first architecture, originally created by Damien Katz at IBM in 2005.
Apache Cassandra is a highly scalable open-source distributed NoSQL database created in 2008 at Facebook by Avinash Lakshman and Prashant Malik, featuring a masterless architecture with linear scalability and high availability.