Was the Transactional Outbox pattern used to guarantee message delivery in Kafka?

Yes, the Transactional Outbox pattern is often used to guarantee message delivery in Kafka and other messaging systems.

Pattern essence:

• Instead of directly sending a message to Kafka within a business transaction, the message is written to a special table (outbox) in the same database where the main transaction occurs.
• After a successful transaction commit, a separate process or service reads new entries from the outbox and sends them to Kafka.
• This ensures that the message is not lost in case of failures and will be sent exactly once, since the outbox record and the business operation are atomic.

Here's an outline of the scheme:

Business operation + writing to outbox (one transaction)
	|
	v
A separate process reads the outbox -> sends to Kafka -> marks the record as sent

This solves the "two-phase commit" problem between the database and Kafka, ensuring data reliability and consistency.