Apache Kafka is an open-source stream-processing software platform developed by the Apache Software Foundation, written in Scala and Java. It is designed to handle data streams from multiple sources and deliver them to multiple consumers. Kafka is used for building real-time data pipelines and streaming applications. It is horizontally scalable, fault-tolerant, incredibly fast, and runs in production in thousands of companies. Kafka acts as a decoupling layer between source and target systems, allowing source systems to produce data into Kafka, and target systems to consume data from Kafka. This makes the architecture more scalable and manageable, as it can handle large volumes of real-time data efficiently.