What Happened While You Were Gone
Decide what you would build from the brief alone. Everything below it is available, but the exercise stops working if you open it first.
A live dashboard updates from a stream. After a laptop wakes from sleep, it shows confidently wrong data until manually refreshed. Design the reconnection and resynchronisation.
Reconnecting and refetching the full snapshot every time, which is simple, always correct, and eliminates the class of bug. It also means every client refetches the entire dashboard simultaneously the moment an office wifi blip resolves — a synchronised, expensive request from every open tab at the same instant, which is how a brief network event becomes a server incident. Full resynchronisation is the right fallback and the wrong default; the cursor exists so the common case is cheap and the expensive path is rare.