Dual Write Problem: Keeping Database Changes and Event Triggers in Sync

Developers often need to perform an action, such as sending an email, immediately after a database change, but the two can fail independently. Wrapping the database insert and the email call in one transaction doesn't work because the email service sits outside the database. Placing a message broker in between still leaves a gap where a failure can occur before the message is published. The commonly recommended fix is the Transactional Outbox Pattern, which writes an event record to an outbox table within the same transaction as the user insert. A separate consumer then reads pending outbox records, triggers the action such as sending an email, and marks each record as processed.