The system constraint questions that should be considered when designing an integration to send orders from Salesforce to a fulfillment system are related to the performance, reliability, and scalability of the integration.
The latency and idempotency of the integration are important factors that affect these aspects. Therefore, the questions A and D are relevant for the integration design. The question B is related to the business logic of the order validation, which is not a system constraint question. The question C is related to the implementation details of the Outbound Messaging interface, which is not a system constraint question either