Composable commerce: picking OMS and fulfilment logic

An OMS chooses fulfilment sources, reserves stock and syncs statuses with carriers and ERP.
When to build custom OMS
Complex cross-border delivery math, split shipments and local customs brokers.
Off-the-shelf OMS licences may hurt at hundreds of thousands of monthly orders.
Front integration
Delivery cost and date must match checkout promises, or complaints spike.
Pre-orders need explicit UI promises.
Edge-case testing
Partial shipments, cancelling one parcel, mid-flight carrier swaps.
Peak simulations with imperfect inventory accuracy.
Frequently asked questions
- Do I always need an OMS?
- No. single warehouses and simple rules often fit the shop engine; OMS appears with scale and many sources.
- How does this pair with Medusa?
- Medusa holds orders; OMS or fulfilment modules extend routing via events and APIs.
- Cross-border VAT?
- Licensed tax rules separate from OMS, otherwise every law change becomes a migration nightmare.
Content updated: March 1, 2026