Description

The Outbox pattern ensures that a database update and sending of a message to a message broker happen atomically. Instead of sending the message directly, the service saves the message into an 'outbox' table in the same database transaction as the business data change. A separate process then reads the outbox and sends the messages.

Where to use

• Reliable messaging in microservices.
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• Avoiding lost messages if the broker is down.
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• Maintaining data integrity between DB and Event Bus.

Real World Example

User Signup: The system inserts the User into the database and a 'WelcomeEmail' event into an 'Outbox' table in the same transaction. A background worker polls the table and sends the email.

Code Example

# Code Concept for Outbox Pattern
# This pattern is architectural.

class Service:
    def execute(self):
        # Implementation logic
        pass