> it expects a level of correct-design-up-front which isn't realistic for most teams. The opposite is true. A non-ES system is an ES system where you are so s

> it expects a level of correct-design-up-front which isn't realistic for most teams. The opposite is true. A non-ES system is an ES system where you are so sure about being correct-up-front that you perform your reduce/fold step when any new input arrives, and throw away the input. It's like not keeping your receipts around for tax time (because they might get crinkled or hard to read, or someone might want to change them).