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Parking Lot System Design
Visual Problem Diagram
Scenario
Saturday mall rush: entry gates disagree with payment kiosks on whether level 3 is full because spot counts updated eventually. The OOD parking lot interview still needs concurrency on spots, ticket state, and payment—at scale add multi-entry coordination.
Design a parking lot system managing entry, spot assignment, hourly pricing, and exit payment. At interview scope start with clear entities and state machines; if scaled, atomic spot assignment prevents double booking.
You should support vehicle entry, spot types, ticketing, payment, and availability display. Be ready to explain concurrency control on spots and fee calculation.
Constraints
Enter/exit, assign spot by type, hourly/dynamic pricing, payment, availability display
No double booking spots, < 2s entry gate response, payment idempotent
Single lot thousands spots; multi-lot city scale shards by lot_id
Stages ahead
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