Your question is Refactor Legacy Without Downtime. 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).
Explain a time you had to refactor a legacy system while maintaining uptime.
Describe the scope of the refactor, how you protected live traffic, and how you coordinated rollback, testing, and stakeholder communication. Focus on the trade-offs you made to reduce risk without slowing delivery.