Citus Data

The company behind citus, now part of microsoft. The repository carries "Copyright © Citus Data, Inc." while adopting the Microsoft Open Source Code of Conduct, and the managed product is sold as Azure Cosmos DB for PostgreSQL — an acquired team still shipping under its own name inside a hyperscaler.

The house style is Postgres extensions. Besides Citus itself, the team maintains pg_cron (cron inside the database), postgresql-hll (HyperLogLog), TopN, pg_auto_failover, and the ORM sharding helpers activerecord-multi-tenant and django-multitenant. Every one of these is a thing Postgres could have absorbed and didn't; the company's bet is that the extension API is a good enough seam to build a distributed database on, and the extension list is that bet made repeatedly.

Set it against planetscale, the spoke's other sharding vendor. PlanetScale ships vitess — a proxy that sits in front of MySQL and reimplements the routing layer. Citus Data ships code that loads into Postgres. Same problem, opposite side of the process boundary, and the consequences for extension and feature compatibility run through both citus and vitess.

Related

citus · microsoft · planetscale · postgresql · operational-databases