If an HTTP call or Kafka send occurs in a transactional method, followed by a database change, what is the potential problem?

The problem is that an HTTP call or sending a message to Kafka is not part of the database transaction, so in case of an error after these actions, data inconsistency may occur. For example, if the HTTP call was successful but the database update failed, the external system will receive the event, while the local database remains in the old state. This violates the atomicity of the operation.

To avoid this problem, patterns like "Outbox" or "Transactional Messaging" are used, where changes are first saved in the database, and then asynchronously sent to external systems, ensuring data consistency.