Apache Pinot is a real-time distributed OLAP (online analytical processing) database. It's built to ingest high-volume streaming data and return sub-second query results. Unlike traditional data warehouses that batch-process data, Pinot ingests data in real-time from Kafka, processes it immediately, and makes it queryable within seconds. Pinot uses a segment-based architecture: data is organized into immutable segments, distributed across a cluster, and indexed for fast queries. It supports SQL syntax, complex aggregations, and GROUP BY operations on billions of rows with latency under one second. Organizations use Pinot to power real-time dashboards, operational analytics, and user behavior insights.