Airbnb developed a stream processing platform called User Signals Platform (USP) to enhance user experience through personalization. The platform leverages user engagement data to provide tailored interactions during the booking process. It consists of a data pipeline layer and an online serving layer, with Flink streaming for near real-time processing and batch processing for data correction and backfill. USP supports various user event processing, including User Signals, User Segments, and Session Engagements. It also uses metrics such as event latency, ingestion latency, job latency, and transform latency to measure the performance of streaming jobs. The platform allows developers to define transforms and user segments without worrying about streaming components. To improve Flink job stability, Airbnb uses standby Task Managers to ensure continuous processing when a Task Manager fails.