ClickHouse

ClickHouse is an open-source column-oriented database management system designed for online analytical processing (OLAP). It specializes in fast, ad-hoc queries over large volumes of data and real-time analytics. The project originated at Yandex and was released as open source in 2016 under the Apache License 2.0. It has since grown into a widely adopted solution in industry, with both community and commercial deployments.

ClickHouse stores data in columns, enabling high compression and efficient reading of only the needed fields. The storage engines in the MergeTree family provide partitioning, primary keys, and data skipping indices, supporting replicated and distributed deployments. Data is written as parts and merged in background processes. The query engine uses vectorized execution and parallel processing across cores and nodes. Features include TTL-based data aging, materialized views, and mutations for updates and deletes, along with support for complex analytical functions, arrays, and nested data.

Deployment scales horizontally through sharding and replication, typically using ZooKeeper for coordination. It is used for real-time analytics on events, logs, metrics, and business data, and is commonly employed for dashboards and BI queries. While optimized for read-heavy analytic workloads, it supports high-throughput ingestion and can operate in on-premises, cloud, or hybrid environments.

Interoperability is provided via native C++ client libraries, HTTP interfaces, and drivers for JDBC/ODBC and languages such as Python and Java. It integrates with visualization and orchestration tools such as Grafana and Apache Superset. The project is maintained by the ClickHouse development community, with governance and professional support offered by commercial entities.