StatsD is a popular daemon that aggregates and summarizes application metrics, allowing developers to instrument their applications using language-specific client libraries. It works by sending individual calls to the StatsD server over UDP datagrams, which are then aggregated and relayed to graphing or monitoring backends. What sets StatsD apart is its simplicity, decoupling of application from instrumentation, tiny footprint, and ubiquity with a wide range of clients and backends available. This allows for easy metrics collection without vendor lock-in, making it an essential part of the modern devops toolchain.