System designEasysd-g533

Subject Parking lotLevel Entry–Mid~30 minCommon in Concurrency interviewsIndustries Software development, Technology

Question

Design the backend for a parking-lot system. The lot has a fixed number of spots in a few size classes (compact, standard, large). When a car enters, the system assigns and reserves a free spot of a fitting size; when it leaves, the spot frees up and a fee is computed from the duration. A display should show how many free spots remain. Cover the data model, how spot assignment works, and how you avoid double-assigning a spot.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.