Your question is Metrics for Phased Rollout Monitoring. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
You're rolling out a new change in stages and need a metric view that helps you decide whether to expand, pause, or reverse the rollout. You want to track early operational signals without losing sight of downstream customer and business impact.
What metrics would you use to monitor a phased rollout of a new operational process or product?