Mock Interviewer
Ask Coach
Tap a question to start, or type your own below.
Booking Waitlist System Design
Visual Problem Diagram
Scenario
A sold-out concert has a huge waitlist. When one ticket is cancelled, the system must offer it fairly, give one user a time-limited window, handle notification delay, and prevent two waitlisted users from accepting the same spot.
Design a booking waitlist for sold-out events or appointments: users join a queue, receive an offer when capacity frees, and get a time-limited window to accept. Fairness and no double-sale are the core requirements.
You should support join, leave, promotion on cancellation, offer notification, accept, decline, expiry, audit, and abuse controls. Be ready to explain why the waitlist can offer a chance, but the booking service still owns inventory truth.
Constraints
Join waitlist, leave waitlist, promote next user, create time-limited offer, notify by channel, accept or decline, expire offer, create booking.
Fair order according to a stated policy, no double booking, durable audit, notification retries, idempotent accept, bounded promotion lag.
Hot resources with hundreds of thousands of waiting users, cancellation bursts, provider notification limits, bots trying to game position.
Stages ahead
Log in to start practicing
Preview the problem below. Sign in to start your timed session, save progress, and use the AI coach.