What is a Kafka message structure?

A Kafka message (record) consists of several fields: Key (optional, bytes): used for partition routing and log compaction. Messages with the same key always go to the same partition. Value (bytes): the actual message payload. Can be any format — JSON, Avro, Protobuf, plain text. Topic: the topic it belongs to. Partition: which partition it is stored in. Offset: its position in the partition. Timestamp: either the producer-set creation time (CreateTime) or the broker-set ingestion time (LogAppendTime). Headers (optional, key-value pairs): metadata about the message — correlation IDs, content type, source system. Serialization: keys and values must be serialized to bytes — use Avro with Schema Registry for schema evolution or JSON for simplicity.