Large spreadsheets need aggressive optimization.
Rendering:
- Virtualize aggressively
- Debounce scroll handlers
- Use CSS containment
Calculation:
- Lazy evaluation (calculate on demand)
- Cache formula results
- Web Workers for heavy computation
Memory:
- Sparse data structure
- Unload distant data
- Compress undo history
Measure: Profile with realistic data. Optimize measured bottlenecks, not assumptions.