Upstream vs Downstream Changes

In any system architecture, some changes cause a cascading series of changes through the system, like knocking down the first domino in a line.

Different design patterns can help minimize the cascade, but when you think about changes with respect to pipelines and data flows, there are “upstream” changes that flow through more of the system than “downstream” changes.

This characterization is typically obvious to developers. Its real value is making it easier to explain change costs to non-engineering groups - sales, customers, executives.