Event Types

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Overview

Event Type	Processing	Use Case
DomainEvent	Processed by event handlers in-process	Domain logic, read model updates
NotificationEvent	Sent to message brokers	Cross-service communication

DomainEvent

Domain events represent something that happened in the domain. They are processed by event handlers:

class UserJoined(cqrs.DomainEvent, frozen=True):
    user_id: str
    meeting_id: str

class UserJoinedEventHandler(cqrs.EventHandler[UserJoined]):
    async def handle(self, event: UserJoined) -> None:
        # Process domain event
        ...

NotificationEvent

Notification events are sent to message brokers:

class UserJoinedNotification(cqrs.NotificationEvent[UserJoinedPayload]):
    event_name: str = "user_joined"
    topic: str = "user_events"
    payload: UserJoinedPayload

# Automatically sent to message broker via EventEmitter

Event Type Comparison

Aspect	DomainEvent	NotificationEvent
Processing	In-process handlers	Message broker
Latency	Synchronous	Asynchronous
Reliability	Immediate	Requires Outbox pattern
Use Case	Domain logic	Cross-service communication