I’m developing inventory management software. Currently I’m researching ways to ensure its impossible to have negative supplies. Given the simplest transactions types like: increase items count for a given item for a given warehouse, reduce it and transfer from one warehouse to another. And the possibility for a user to create, delete and update those transactions, including dates, items lists, quantities and warehouses – I can see no other way rather than on each change to recalculate entire set of transactions for given items+warehouses. However it is obviously not a scalable way to manage this.