This document discusses Apache IoTDB, an open source time series database for industrial IoT applications. It describes the origins and goals of IoTDB in managing the large volumes of time-oriented machine data produced by IoT devices. Key features of IoTDB include efficient storage and querying of time series data, native support for time series operations, and integration with common data analytics ecosystems. The document outlines IoTDB's architecture, data model, query language, optimized TsFile data format, and encoding schemes.