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Design an in-memory hotel booking system

ImcSoftware Engineer · Technical Screen
MediumSoftware EngineerTechnical ScreenSystem Design

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This question evaluates a candidate's ability to design in-memory data models, concurrency control mechanisms, and temporal reservation logic for booking systems.

Design a hotel booking system that supports reservations without using any database. You may only use in-memory data structures.

Requirements

Define APIs/data structures to support at least:

  • Add hotels, room types, and room inventory (or individual rooms)
  • Search availability for a date range (check-in, check-out)
  • Create a booking (reserve room(s))
  • Cancel a booking
  • Prevent double-booking under concurrent requests

Constraints/notes

  • All state is in memory (assume a single process unless you choose to extend to multiple nodes).
  • Clarify assumptions (e.g., time zones, check-out exclusivity, maximum date horizon).
  • Discuss complexity trade-offs and how you would handle concurrency.