This document discusses the need for a time series database and introduces OpenTSDB as an option. Some key points: - Time series data is useful for analyzing metrics and patterns over time but is currently scattered across different databases. - OpenTSDB is an open source time series database that can store trillions of data points, scale using HBase, and never loses precision. - It is optimized for write throughput and can handle thousands of data points per second. Reads depend on the cardinality of metrics but it supports time-based queries. - OpenTSDB uses HBase under the hood and stores tags with metrics to allow for flexible filtering of time series data without affecting performance.