Apache Flink is a distributed stream processing framework designed for high-throughput, low-latency data processing over unbounded and bounded data streams. Operating at the heart of real-time data pipelines since its Apache Software Foundation graduation in 2014, Flink delivers exactly-once processing semantics and event-time semantics that handle out-of-order events with precision. Unlike batch-first frameworks retrofitted for streaming, Flink was architected from the ground up for continuous computation—meaning stateful operators, time-based windows, and fault tolerance via distributed snapshots aren't afterthoughts but core primitives that enable applications to run for months without human intervention while processing trillions of events.