Neo4j is a graph database management system developed by Neo4j, Inc based in the San Francisco Bay Area, USA. Described by its developers as an ACID-compliant transactional database with native graph storage and processing, Neo4j is the most popular graph database according to DB-Engines ranking, and the 22nd most popular database overall. It’s an open-source Database.
Licensing and editions
Neo4j comes in 2 editions: Community and Enterprise. It is dual-licensed: GPL V3 and a commercial license. The Community Edition is free but is limited to running on one node only due to the lack of clustering and is without hot backups.
The Enterprise Edition unlocks these limitations, allowing for clustering, hot backups, and monitoring. The Enterprise Edition is available under a closed-source Commercial license.
Evolutions of Neo4j
Version 1.0 was released in February 2010.
Neo4j version 2.0 was released in December 2013.
Neo4j version 3.0 was released in April 2016.
In November 2016 Neo4j successfully secured $36M in Series D Funding led by Greenbridge Partners Ltd.
In November 2018 Neo4j successfully secured $80M in Series E Funding led by One Peak Partners and Morgan Stanley Expansion Capital, with participation from other investors including Creandum, Eight Roads and Greenbridge Partners.
A graph database is used to represent relationships. The most common example of that is the Facebook Friend relationship as well as the Like relationship. You can see some of that in the graphic below from Neo4j.
The circles are nodes. The lines, called edges, indicate relationships. And the any comments inside the circles are properties of that node.
Image source: Neo4j
A remote Neo4j Server can be accessed via its Cypher HTTP API, either directly or through one of the many available language drivers. For especially high performance use cases, you can add Neo4j Server extensions in any JVM language to access Neo4j’s internal database engine directly without network overhead.