Spreadsheets have enormous scope. Define boundaries early.
Functional requirements:
- Display grid of cells (rows and columns)
- Edit cell values (text, numbers)
- Basic formulas (SUM, AVERAGE)
- Cell selection (single, range)
- Copy/paste cells
Non-functional requirements:
- Handle million+ cells
- Smooth scrolling at fps
- Keyboard-driven workflow
- Undo/redo support
Scope for interview: Focus on rendering and editing. Defer charts, conditional formatting, and collaboration.