Kafka producers and consumers are the two client roles that write to and read from Kafka topics — producers publish records, and consumers subscribe to topics to process the data producers send.
Key Points: • Producers serialize and send records to a specific topic, optionally targeting a partition using a record key. • Consumers subscribe to one or more topics and pull records from the partitions assigned to them. • Consumers are typically organized into consumer groups so that work on a topic can be parallelized across multiple instances. • Producers and consumers are decoupled in time — a consumer doesn't need to be running when a producer sends a message, since Kafka persists it until it's read or retention expires.
Example: A ride-sharing app's driver-location service acts as a producer, continuously publishing GPS updates to a "driver-locations" topic, while a separate matching service acts as a consumer, reading those updates in real time to pair drivers with nearby riders.
Interview Tip: A concise interview answer is:
"Producers are client applications that publish records to Kafka topics, and consumers are client applications that subscribe to those topics and process the records, usually as part of a consumer group so the work can be parallelized, and because Kafka persists data, producers and consumers don't need to be online at the same time."