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ClickHouse

ClickHouse is an open-source columnar database built for extremely fast analytical queries over huge datasets, maintained by ClickHouse Inc. It sits around #24 in real-world usage (roughly 2.4%, tied with Valkey), often used to power real-time dashboards where traditional row-based databases get too slow.

📌 Quick facts
Type: Columnar analytical database (OLAP)
Made by: ClickHouse Inc.
License: Free/open-source core, with paid cloud tier
Hosting: Self-hosted or cloud-managed
Primary use case: Real-time analytics dashboards over very large datasets

Core concepts & example

ClickHouse uses standard SQL, but stores data column-by-column rather than row-by-row, which makes aggregate queries over huge tables extremely fast:

SELECT toDate(event_time) AS day, count() AS events
FROM page_views
WHERE event_time >= now() - INTERVAL 7 DAY
GROUP BY day
ORDER BY day;

Getting started

ClickHouse runs as a standalone server, easiest to try locally via Docker:

# run ClickHouse locally via Docker
docker run -d --name clickhouse -p 8123:8123 -p 9000:9000 clickhouse/clickhouse-server

🎯 Best for: real-time analytics dashboards and event-log analysis over very large datasets.