Exam Certified Integration Architect topic 1 question 21 discussion

A company has an external system that processes and tracks orders. Sales reps manage their leads and opportunity pipeline in Salesforce. In the current state, the two systems are disconnected and processing orders requires a lot of manual entry on the sales rep part. This creates delays in processing orders and incomplete data due to manual entry.
As a part of modernization efforts, the company decided to integrate Salesforce and the Order Management System. The following technical requirements were identified:
1. Orders need to be created in real time from Salesforce.
2. Minimal customizations and code should be written due to a tight timeline and lack of developer resources.
3. Sales reps need to be able to see order history and most up-to-date information on current order status.
4. Managers need to be able to run reports in Salesforce to see daily and monthly order volumes and fulfillment timelines.
5. The legacy system is hosted on-premise and is currently connected to the Enterprise Service Bus (ESB). The ESB is flexible enough to provide any methods and connection types needed by the Salesforce team.
6. There are 1,000 sales reps. Each user processes/creates on average 15 orders per shift. Most of the orders contain 20 to 30 line items.
How should an integration architect integrate the two systems based on the technical requirements and system constraints?