How would you implement a master-detail page where a list item opens a detail panel or detail route?

In production I would tune for perceived performance and data privacy. A split route can support SSR for detail pages, while a side panel can feel faster for admin workflows. The design needs clear behavior when filters remove the selected item, when another user deletes it, or when permissions change. I would monitor list latency, detail latency, cache hit rate, 404/403 detail responses, and over-fetching through payload size. I would add regression coverage for deep links and permission changes because those are the cases that often break after route or cache refactors.