Kafka Events

An Event is any type of action, change or incident that is identified or recorded by software or applications.

Event is a combination of

• notification: when-ness that can be used to trigger some other activity
• state: fairly small and usually represented in structured format.

Kafka models events as key/value pairs. Values are typically the serialized representation of an application domain object or some form of raw message input, like the output of a sensor.

Keys can also be complex domain objects but are often primitive types like strings and integers. The key part of a Kafka event is not necessarily a unique identifier for the event, like the primary key of a row in a relational database would be. It is more likely the identifier of some entity in the system, like a user, order, or a particular connected device.