Citus Data

Overview

Citus Data made PostgreSQL scale across machines without asking developers to abandon PostgreSQL. Its software sharded distributed tables, replicated reference data, and routed or parallelized queries across a cluster. The decisive architectural move was turning Citus from a PostgreSQL fork into an extension, then releasing the core as open source.

The company sold enterprise software and a managed cloud service around that extension. It raised a $9.5 million Series A in 2015, opened engineering offices in Istanbul, San Francisco, and Amsterdam, and became part of Microsoft in January 2019. Microsoft integrated the technology into Azure's PostgreSQL offerings while the Citus project continued in public.

Citus did not fail as a product. The acquisition ended the independent company and moved its commercial platform into a hyperscale cloud provider. Its history shows how an infrastructure startup can reduce adoption risk by aligning with an established open-source system, then become strategically valuable to a platform that needs a credible managed version.

Founding Story

Umur Cubukcu, Sumedh Pathak, and Ozgun Erdogan met in graduate school at Stanford. Erdogan and Pathak later worked as engineers at Amazon, while Cubukcu joined Boston Consulting Group. Their shared frustration came from NoSQL architectures that gained scale by giving up familiar relational features.

The founders wanted horizontal scale without abandoning transactions, joins, foreign keys, SQL, and the PostgreSQL ecosystem. Rather than write an unrelated database, they built on PostgreSQL. They founded Citus Data in January 2011, moved to Istanbul to open the first office, and joined Y Combinator's Summer 2011 batch.

The early product was called CitusDB. MixRank became its first production user in July 2012. Headquarters moved to San Francisco in 2013, while the Istanbul engineering base remained part of the company. That split gave Citus a durable technical center and access to US customers and capital.

Timeline

• January 2011: Cubukcu, Pathak, and Erdogan founded Citus Data and opened an office in Istanbul.
• June 2011: The company joined Y Combinator's Summer batch.
• July 2012: MixRank put the first Citus deployment into production.
• March 2013: Citus Data moved its headquarters to San Francisco.
• 2014: The team released the cstore_fdw columnar-store extension and later the open-source pg_shard extension.
• October 2015: Citus Data raised a $9.5 million Series A led by Khosla Ventures.
• March 2016: The company refactored Citus from a PostgreSQL fork into an extension and released Citus 5.0 as open source.
• July 2016: Citus Cloud became generally available on AWS.
• May 2018: Citus opened an engineering office in Amsterdam.
• January 24, 2019: Microsoft acquired Citus Data for undisclosed terms.
• 2022: Microsoft and the Citus team open-sourced the remaining enterprise features in Citus 11.

What They Built

Citus transforms PostgreSQL into a distributed database. Large tables are split into shards and placed across worker nodes. Reference tables can be copied to every node. A distributed query engine directs work to the relevant shards and combines results, allowing the cluster to use more CPU, memory, storage, and input-output capacity than one server.

The product initially lived as a PostgreSQL fork. That gave the team deep control but imposed a recurring compatibility burden when PostgreSQL changed. In 2016 Citus “unforked” the codebase and delivered it as an extension. Existing PostgreSQL users could add distributed behavior while continuing to use familiar drivers, SQL, monitoring, and administration practices.

Citus Data offered three consumption paths: an open-source extension, enterprise software for customer-managed deployments, and Citus Cloud as a managed service. This structure converted community adoption into commercial opportunities without making a proprietary database the only way to try the technology.