Apache Kafka is preferred when you need reliable message streaming with high throughput and durability. You would use it when you want to build a data pipeline for real-time analytics, particularly when the system must handle varying loads without dropping messages. For example, if you are developing a log aggregation system where applications send logs to Kafka for later processing and analysis, Kafka is ideal because it can efficiently handle high volumes of log data and ensure message retention.
Apache Storm is preferred when you need to perform complex real-time computations on streaming data with low latency. You'd use Apache Storm in scenarios where you must process and analyze live data streams instantaneously, such as in a real-time fraud detection system, where you need to evaluate transactions as they occur.