DevOps engineers are tasked with developing an order processing system designed to notify relevant departments each time an order is placed. Alongside this, the system needs to push identical notifications to a processing module, enabling EC2 instances to handle order fulfillment. Additionally, it must support message re-processing in the event of errors and allow the system to scale transparently without necessitating manual or programmatic resource provisioning.

Which of the following solutions can be used to address this use-case in the most cost-efficient way?