Design a parking lot system

Design a parking lot system (software + core components) that supports multiple entry/exit gates, different spot types, ticketing, and payment.

Functional requirements

• Vehicles enter via an entry gate and receive a ticket.
• Vehicles park in an appropriate available spot (e.g., compact/large/EV/handicap).
• Vehicles exit via an exit gate and pay based on time parked (and possibly vehicle/spot type).
• The system should:
  • Track spot occupancy and availability in near real-time.
  • Handle multiple floors/zones.
  • Support lost-ticket scenarios and payment failures.

Non-functional requirements

• Correctness under concurrent arrivals/departures.
• High availability for gate operations (tickets and exits should still work during partial outages).
• Low latency at gates (avoid long lines).
• Auditable records for payments and occupancy.

Provide:

• High-level architecture
• Core data model
• Key APIs
• Main flows (enter, park, exit, payment)
• Concurrency/consistency approach and failure handling