DeepL is a company that uses ClickHouse as its central data warehouse to support various use cases such as analytics, company metrics, and technical monitoring. The company started using ClickHouse in 2020 to build up its analytics capabilities in a privacy-friendly manner, initially setting up a single node setup that proved capable of handling the amount of data they were throwing at it. They later invested heavily in automation, creating a combined source of truth for all events and table schemas, which enabled them to create complex events and queries that understood how users interacted with their platform. With this foundation, DeepL expanded its cluster from a single node setup to a more robust configuration, ingesting half a billion raw rows per day. They also utilized ClickHouse for experimentation, using it as the statistical analysis engine for AB-testing, which allowed them to rapidly iterate on frontend and algorithmic backend changes. Additionally, ClickHouse was used in their ML-infrastructure of personalization, serving as the data store for training and inference models based on user history.