Our Chief Scientist Martin Fowler recently discussed the architecture of GAP Inc.'s purchase order system, SCMS PO. Read a snippet below or view the full info deck on martinfowler.com.
Its purpose is to help Gap Inc. manage purchase orders from suppliers. (SCMS stands for "supply chain management system".)
Purchasing staff can put purchase orders (PO) on-screen and make changes depending on the state of the PO.
Business logic includes validation of changes and figuring out consequences such as delivery routing and allocation of demands across suppliers.
SCMS PO supports a separate service that takes demand orders from upstream forecasting systems and turns them into purchase orders. (An example might be a demand for 100 red T-shirts which SCMS PO might split 60:40 into POs against different suppliers according to its allocation rules.) This demand order service is only an API.
There are a few dozen users, scattered around the globe.
Much of the talk about web applications centers on dealing with public-facing systems that must handle large volumes of users, but most corporate systems have much lower and constrained loads.
On a typical day, 20-30 POs will be updated.
On peak days about 200-300 POs will get updates
The architecture is designed to handle loads one order of magnitude greater than these.