I've written a fulfillment engine before. It is complicated and generally does not lend itself to reuse. The reason is because the problem space is usually very

I've written a fulfillment engine before. It is complicated and generally does not lend itself to reuse. The reason is because the problem space is usually very specific. Building a general solution that fits everyone is near impossible. That said Amazon actually has a Fulfillment API. The real trick is integrating your fulfillment into all your other business processes.