44/60 Days System Design Questions (opens in new tab)

Your team just shipped "offline mode" for your field-service app. Technicians work in basements, tunnels, plant floors — connectivity is unreliable. The demo looked great. Navigator.onLine said false, the app kept working, the sync button pulsed green. You shipped to 400 users. Then the incident reports started. Technician in Munich finishes a repair job offline, syncs when she gets signal. Her updates are gone — overwritten by a colleague who edited the same record online 12 minutes earlier....