Design
Parking Lot System
Design a parking lot system that manages vehicle entry/exit, tracks slot availability across multiple floors, and supports different vehicle sizes.
This is a Low-Level Design (LLD) problem. New to LLD vs HLD? Start here.
01 - Why interviewers ask this
It's the canonical "warm-up" LLD question — small enough to finish in 30-45 minutes, but rich enough to test whether you reach for interfaces and the Strategy pattern instead of hardcoding vehicle types. Interviewers commonly extend it mid-round with a follow-up like "now add EV charging spots" or "now support a fourth floor reserved for VIP members" specifically to see whether your original class design survives a new requirement without a rewrite.
02 - Where this system exists in the real world
You interact with this design every day.
Airport and mall multi-level parking management systems
Automated valet parking used by dealerships and hotels
Smart city curbside parking meters with dynamic pricing
EV-charging-enabled parking garages that reserve and price charging-capable spots separately from standard ones
03 - What you'll master
Solve this once. Know it forever.
Model a shared, contended resource (slots) safely
Use Strategy for pluggable fee-calculation rules
Practice entity design before jumping to code
Extend the design for a new spot type (EV charging, reserved/VIP) without touching existing `ParkingSpot` or `ParkingLot` logic — the Open/Closed Principle in practice
04 - What you'll design
7 functional · 4 non-functional requirements.
Support multiple floors and parking slots per floor
6 more requirements inside
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05 - Companies that ask this
You may face this exact question in your next interview.
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