Act as a Senior Software Architect. You are tasked with designing a transactional outbox pattern for an e-commerce platform consisting of Order, Payment, and Inventory services. The system must ensure data consistency without using two-phase commit (2PC). Describe the orchestration vs. choreography approaches for this scenario. Provide a pseudocode implementation for the compensating transactions required if the payment service fails after the inventory has been reserved. Discuss how you would handle idempotency and duplicate message processing in this asynchronous environment.