I’m designing the payment and shipping lifecycle for a physical-goods marketplace and would appreciate feedback from backend / systems architects.

Note: Follow the notations  
Image 1: Buyer doesnot returns the order  
Image 2: Buyer returns the order

**Context:**

* Marketplace model (buyer → escrow → seller)
* Shipping via UPS (API-based integration)
* Master carrier account (v1)
* Escrow held until delivery + return window closes
* Return flow supported
* Push-based tracking (UPS Track Alert style events)



# High-Level Flow

1. Buyer places order → payment held in escrow
2. Seller notified and accepts order
3. Marketplace creates shipment (UPS API)
4. Label generated → seller prints + hands to carrier
5. Tracking updates drive internal shipment state
6. Item delivered
7. Return window (N days)
8. If no return → escrow released to seller
9. If return initiated → reverse logistics + settlement adjustment



# Design Considerations

* Shipment state machine (created → in transit → delivered → exception → closed)
* Webhook/push tracking integration
* Escrow payout release timing
* Seller packing SLA (X days before auto-cancel)
* Return flow & reverse pickup scheduling
* Handling delivery exceptions
* Who absorbs dimensional weight surcharge deltas
* Pausing payout on exception/claim



# What I’m Looking For

* What failure states am I missing?
* Is delivery-based escrow release sufficient, or should there be additional buffers?
* Any major financial risk exposure in this model?
* Would you recommend push tracking only, or hybrid polling fallback?
* What would you simplify for MVP?

Designing Escrow + Shipping Lifecycle for a Marketplace Project (UPS Integration) – Architecture Feedback Requested