Citus - Scalable PostgreSQL for multi-tenant and real-time workloads

Citus is a distributed database that scales across commodity servers using transparent sharding and replication. Citus extends the underlying database rather than forking it, giving developers and enterprises the power and familiarity of a relational database. As an extension, Citus supports new PostgreSQL releases, and allows you to benefit from new features while maintaining compatibility with existing PostgreSQL tools.

Citus is a PostgreSQL extension and not a fork. It is scalable across multiple machines through sharding and replication. It supports distributed engine for query parallelization.