Structuring what flows.
WHAT EVERY EVENT SHOULD CARRY
A unique identifier The event type When it occurred The entity it concerns The payload A schema version
WHY THE IDENTIFIER MATTERS
It is what makes consumers idempotent.
WHY THE VERSION MATTERS
Consumers must handle events produced before a change.
WHAT EVENT DESIGN APPROACHES EXIST
- Notification: something happened, with an identifier to look up
- State transfer: the full new state
- Delta: what changed
WHAT NOTIFICATION SUITS
Loose coupling, where consumers fetch what they need.
WHAT STATE TRANSFER SUITS
Consumers that must not depend on the source being available.
WHAT TO PREFER FOR ANALYTICAL CONSUMPTION
State transfer, since it is self-contained and replayable.
WHAT SCHEMA EVOLUTION RULES TO FOLLOW
Adding optional fields is safe Removing or renaming fields is not Changing types is not
WHAT A SCHEMA REGISTRY PROVIDES
Central schemas, with compatibility checked before producers publish.
WHY THAT MATTERS
It prevents a producer breaking every consumer.
WHAT TO NEVER PUT IN AN EVENT
Sensitive data that consumers do not need.
WHY
Events are retained and widely readable.
