ClickHouse / Real-Time OLAP
Also written as ClickHouse, Apache Druid, Apache Pinot, StarRocks, Real-Time OLAP
Very fast analytical databases that answer questions over billions of rows in under a second, often on data that arrived moments ago. Used behind live dashboards, product analytics and observability tools. ClickHouse is the best known; Apache Druid, Apache Pinot and StarRocks do similar jobs.
Think of it like
A scoreboard that totals the whole season instantly, updated as each point is scored.
Junior or senior?
Senior sounds like
Can explain why they needed this instead of a warehouse like Snowflake or BigQuery (usually speed or cost at high query volume) and how they shaped the data to keep queries fast.
Ask them
“Why did your team need ClickHouse instead of your existing warehouse, and what did you change to keep queries fast?”