The PreBus validates the request for all inputs and passes the control back to the user with success or failure of the execution of the input. In case of eventual consistency, the Services makes sure that the data is put into the chosen Bus. Further, if you don't want eventual consistency and don't want to put the data into the bus for processing in an asynchronous manner, PreBus takes care of that. It also provides the option to store data or interact with the database directly without skipping the bus.