[CouchDB](https://couchdb.apache.org) - a multi-master NoSQL database management system with robust replication.

[hharng]

It is relatively easy to create a multi-master database cluster on cheap virtual machines which can be geographically globally distributed and even multi-cloud: for example, 1 VPS from Hetzner in Germany, 1 VPS from OVH in Canada and 1 VPS from AWS in the USA; the replication "just works", and the individual instances and the whole cluster repair themselves quite well, unlike, for example, MongoDB, which can becomes unusable after an unexpected shutdown and restart.