Solutions rarely fail on features — they fail on the things nobody wrote down. Non-functional requirements (NFRs) are those quality attributes, and pinning them down early is what keeps a design honest.
Non-functional requirements describe how well a system must behave, rather than what it does. They're the difference between "it works on my machine" and "it works for 10,000 users at month-end".
An NFR you can't measure can't be met. "Fast" is not a requirement; "95% of requests under 500ms at 1,000 concurrent users" is. Attach a number and a way to verify it to every NFR.
NFRs are cheapest to meet when they shape the design, and most expensive to retrofit after go-live. Capture them at the start of the review, not the end.
The Architecture Review Kit includes an NFR assessment template that turns quality expectations into measurable, testable targets — and feeds the scorecard and report.
