A message (also referred to as a record or event) is the smallest unit of data in Kafka. Each message consists of a key, value, timestamp, and metadata. Messages are stored in partitions and are identified by their offsets.
From Kafka documentation:
“The atomic unit of data in Kafka is a message, which includes a key, value, and headers.”
A → Logical grouping of messages.
B → Correct: Base-level data structure.
C → A topic holds partitions, not messages directly.
D → Refers to the position of a message, not the message itself.
Page Reference:
Kafka: The Definitive Guide, 1st Edition, Chapter 4, p. 120
Apache Kafka Documentation: Message Structure