About ClickHouse
The columnar OLAP database built for real-time analytics on huge tables.
ClickHouse started inside Yandex in 2009 as an internal analytics engine for Yandex Metrica, the company's web-analytics product. It was released as open-source software under the Apache 2.0 license in 2016, and ClickHouse Inc was incorporated in San Francisco in September 2021. The company now ships the open-source database alongside ClickHouse Cloud, a managed offering on AWS, GCP and Azure.
The architectural choice that defines ClickHouse: columnar storage with vectorized execution. Tables are stored column by column on disk, queries read only the columns they touch, and the engine processes data in batches that map cleanly onto modern CPU instructions. The MergeTree family of table engines layers a sparse primary-key index on top, with granules of 8,192 rows by default, which is what lets a single server scan billions of rows in a second or two. The flip side is that the design choices made on day one (the ORDER BY key, the partition expression, the compression codec) decide how the warehouse performs six months later, when the table is at 50 billion rows and the queries that used to return instantly now scan the whole thing. We land the data, model it for the queries you run in production, and pick the engine settings so ClickHouse stays in its sub-second sweet spot instead of degrading into a slow scan engine.