Top 3 multi-master open source projects

OrientDB is the most versatile DBMS supporting Graph, Document, Reactive, Full-Text and Geospatial models in one Multi-Model product. OrientDB can run distributed (Multi-Master), supports SQL, ACID Transactions, Full-Text indexing and Reactive Queries. OrientDB Community Edition is Open Source using a liberal Apache 2 license.

An open-source database designed to support multi-master replication. It is designed on the top of PostgreSQL, providing bidirectional replication, as well as row filtering.

Multi-master Kubernetes cluster on Exoscale