I feel like Sheets should gracefully fail much better than it does under load, especially for supposedly being Google-scale. With more users, instead of not loading at all, or starting then failing to load, it would be nice to see the most recent change in read-only mode, and show an edit timeline like the Internet Archive's Wayback Machine UI shows archive occurrences on a calendar. Just a couple ideas for how Sheets could break down gracefully while retaining usability.