This document discusses Apache Flink, an open source stream processing framework. It provides an overview of Flink and how it enables low-latency stream processing compared to traditional batch processing systems. Key aspects covered include windowing, state handling, fault tolerance, and performance benchmarks showing Flink can achieve high throughput. The document demonstrates how Flink addresses challenges like out-of-order events, state management, and exactly-once processing through features like event-time processing, managed state, and distributed snapshots.