Postgres is the endgame database. Gel supercharges it with a modern data model, graph queries, Auth & AI solutions, and much more.

CouchDB is described as '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' and is a relational database in the development category. There are more than 50 alternatives to CouchDB for a variety of platforms, including Linux, Windows, Mac, Self-Hosted and Web-based apps. The best CouchDB alternative is PostgreSQL, which is both free and Open Source. Other great apps like CouchDB are MySQL Community Edition, MongoDB, MariaDB and Redis.
Postgres is the endgame database. Gel supercharges it with a modern data model, graph queries, Auth & AI solutions, and much more.

CUBRID is a comprehensive GPL/BSD open source relational database management system highly optimized for Web Applications. CUBRID is being developed in C/C++. Includes native HA, online hot backup, and other features. JDBC, PHP, ODBC/.NET, Ruby & Python APIs.