Question 8. Is it possible to use the @Transactional annotation on the handle method of ExampleService to ensure consistency?

The @Transactional annotation in Spring manages database transactions, ensuring atomicity of database operations within a single service.

In this case, the ExampleService::handle method calls orderDao.delete — a database operation, and deliveryService.cancelDelivery — an HTTP call to another service.

The problem is that the @Transactional transaction does not extend to external HTTP calls. If deliveryService.cancelDelivery throws a RuntimeException, the transaction that deletes the order in the database will roll back, and the order will not be deleted.

However, if deliveryService.cancelDelivery fails after the order has been deleted, the transaction will roll back, and the user will be informed that the order was not deleted.

Therefore, the answer is:

• Yes, in case of a database change error, the changes will be rolled back.

But it is important to understand that @Transactional does not provide distributed transactionality between services. For consistency between services, other patterns are needed (e.g., sagas, compensating transactions).

Other answer options are not correct:

• The user learns about the error because a RuntimeException is thrown.
• Memory leaks and timeouts are not directly related to @Transactional.

Summary: Using @Transactional here is possible and will roll back database changes on error, but it does not guarantee consistency between services.