DuckDB: An OLAP Query Engine Inside Your Process
DuckDB is an in-process columnar OLAP database for Parquet, CSV, and DataFrames, not a conventional multi-user OLTP server for web applications.
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3 postsMetrics & Analytics Interview Guide: From North Star to Experiment Design
Metrics interviews test whether you can make decisions with numbers, not how much statistics you know. Core skills: north star metric selection logic (why this one and not that one), metric tree decomposition (finding actionable levers), funnel analysis (which step's drop-off is most worth fixing), A/B testing design and pitfalls, and judgment when facing counterintuitive data.
ClickHouse: When PostgreSQL Analytics Queries Start Slowing Down, You Need OLAP
ClickHouse is a column-oriented OLAP database that scans hundreds of millions of rows in seconds. DaoDao uses it to record user behavior events for the AI recommendation engine's feature engineering, letting PostgreSQL focus on transactional data.