Hint 1 — locked

Hint 2 — locked

Hint 3 — locked

Problem

Build a system for a multi-level parking lot. Vehicles enter and exit; the system tracks available spots in real-time, assigns the nearest available spot, and processes payments on exit. Multiple parking lots may be managed by the same platform.

Functional Requirements

• Track available spots by type (compact, large, handicapped, motorcycle)
• Assign nearest available spot when a vehicle enters
• Calculate fee based on duration and vehicle type on exit
• Support multiple lots with independent spot inventories
• Generate receipts and support online pre-booking

Non-Functional

• 1,000 concurrent vehicles per lot, up to 500 lots
• < 200 ms spot assignment latency
• 99.9% availability — entry/exit must never be blocked
• Spot state must be consistent — no double-assignments

Prerequisites