Vaccine Booking System Design
Visual Problem Diagram
Scenario
Appointment slots open at 8am and 300K seniors refresh together—without a virtual queue and sharded inventory, the site shows available slots that vanish at checkout. Fair access, slot holds, and identity rules dominate over drawing forms.
Design a vaccine (or high-demand medical) appointment system with location-based slots, eligibility rules, and extreme contention at release time. Public trust requires fair access and no double-booking.
You should support slot search, book/reschedule/cancel, reminders, and waitlist optional. Be ready to explain admission control, hold/confirm, and eligibility.
Constraints
List slots by site, book/reschedule/cancel, eligibility check, reminders, waitlist optional
Fair admission under flash load, zero double book, 99.9% availability, accessible UX
Millions users, thousands sites, flash 100K RPS on open, mostly read before write spike