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Design a restaurant reservation system

C3 AISoftware Engineer · Onsite
EasySoftware EngineerOnsiteSystem Design

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This question evaluates skills in system architecture and engineering, including data modeling, API design, concurrency control to prevent double-booking, availability and scheduling logic, scalability under traffic spikes, and operational concerns like auditability and low-latency queries.

Problem

Design a restaurant reservation system similar to common booking products.

The system should allow customers to search availability and book tables at a restaurant, and allow the restaurant to manage tables and reservations.

Core requirements

Customer-facing

  • View a restaurant’s availability for a given date/time and party size.
  • Create a reservation (name/contact, party size, desired time, special notes).
  • Modify/cancel a reservation.
  • Receive confirmation and reminders (email/SMS/push).

Restaurant-facing

  • CRUD restaurants, operating hours, blackout dates/holidays.
  • Configure table inventory (table IDs, capacities, combinable tables).
  • View upcoming reservations; mark no-shows/seated/completed.

Non-functional requirements

  • Prevent double-booking (correctness is critical).
  • Low latency for availability lookup (e.g., p95 < 200–300ms).
  • Handle spikes (e.g., lunch/dinner hours, popular restaurants).
  • Auditability (who changed/cancelled what) and idempotent APIs.

Assumptions (state clearly)

  • Multi-restaurant platform (many restaurants).
  • Reservations are time-bound (e.g., 90-minute default duration, configurable).
  • Timezone-aware scheduling.

What to cover in your design

  • Data model (tables/reservations/locks/slots).
  • APIs and main flows (search availability → book → confirm → remind).
  • Concurrency control strategy to avoid double-booking.
  • Scaling approach and caching strategy.
  • Edge cases: cancellations, no-shows, walk-ins, table combinations, overbooking/waitlist.