Functional Requirements

A parking lot system must handle:

• Vehicle entry and exit: Cars, motorcycles, trucks, and possibly electric vehicles.
• Slot allocation: Assign available slots efficiently to incoming vehicles.
• Ticketing: Generate a ticket with entry time, vehicle ID, and slot details.
• Payment processing: Calculate fees based on time parked or flat rates.
• Slot availability tracking: Update real-time status as vehicles enter or exit.
• Validation: Ensure only valid tickets allow exit.

Non-Functional Requirements

Beyond basic functionality, the system should also ensure:

• Scalability: Support anything from a 50-slot local lot to a 10,000-slot multi-level garage.
• Fault tolerance: Work smoothly even if a kiosk or server goes down.
• Reliability: Ensure no double-booking of slots and no loss of payment records.
• Low latency: Entry and exit flows should be fast to avoid congestion.
• Usability: Easy for drivers and operators to interact with (self-service kiosks, apps, etc.).

Assumptions

To simplify, let’s assume:

• Each slot can only fit one vehicle at a time.
• Vehicles fall into broad categories (motorcycles, cars, trucks).
• Payment is calculated on duration unless otherwise stated.
• Parking can be tracked via tickets or license plate recognition.

API Design

Define the APIs expected from the system. This is your chance to analyze and define the read and write paths so that you can come up with the high-level design...

High-Level Design

Core Components of Design a Parking Lot System Design

1. Entry/Exit Gates
   • Equipped with kiosks, sensors, or license plate recognition.
   • Trigger slot allocation and ticket generation at entry.
   • Validate ticket and payment at exit.
2. Ticketing System
   • Issues tickets (paper, QR code, or digital).
   • Associates tickets with vehicles, slots, and timestamps.
   • Prevents fraudulent exits by linking tickets to actual usage.
3. Slot Management Module
   • Tracks real-time slot availability.
   • Allocates slots based on rules (nearest to exit, vehicle type, or first available).
   • Updates availability when vehicles enter or leave.
4. Payment Processor
   • Calculates parking fees based on duration or flat rates.
   • Integrates with cash, cards, or digital payment options.
   • Ensures secure, auditable transactions.
5. Database and Backend Services
   • Store vehicle records, ticket history, payment logs, and slot data.
   • Provide APIs for mobile apps or operator dashboards.
   • Use replication and backups to prevent data loss.
6. Admin/Monitoring Dashboard
   • Lets operators monitor occupancy in real time.
   • Provides analytics on usage patterns, revenue, and peak hours.

Data Flow Example

1. A car approaches the entry gate.
2. The system checks for available slots.
3. A ticket is issued, and the slot is reserved.
4. The car parks in the assigned slot.
5. Upon exit, the ticket is validated, payment is processed, and the slot is released.

Detailed Component Design

Deep dive into 2-3 key components. Explain how they work, how they scale, discuss tradeoffs, capacity, and any relevant algorithms or data structures.