Your question is Efficiently Render Thousands. 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).
How would you architect a component that needs to render thousands of items efficiently?
Explain how you would structure rendering, scrolling, data loading, updates, and user interactions. Discuss the performance tradeoffs of virtualization, pagination, incremental rendering, memoization, and client-side caching, along with how you would measure and monitor the result in production.