Your question is Capacity Planning in the Cloud. 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).
Describe how you approach capacity planning for rapidly scaling cloud infrastructure.
Explain the assumptions, data, forecasting method, and stakeholder decisions you would use. Cover cost, performance, reliability, scaling triggers, dependencies, and how you would validate the plan during execution.