Requirements

Assign parking spots based on vehicle size, allowing motorcycles to park in small spots, cars in medium spots, and trucks in large spots, with the option to park in larger spots if needed.
Issue a ParkingTicket upon vehicle entry, which records the vehicle information, assigned parking spot, and entry timestamp.
Compute the parking fee upon vehicle exit based on the duration of stay and a configurable pricing strategy.
Handle scenarios where the parking lot is full by rejecting entry and displaying a lot-full indicator to the driver.
Support multiple floors in the parking lot, with each floor containing a mix of small, medium, and large parking spots.

List the key non-functional requirements (eg thread safety, extensibility, maintainability, etc.)...
Ensure thread safety and concurrency control to prevent race conditions during parking spot allocation and ticket processing.
Ensure high performance with efficient data structures for fast lookup of available spots and ticket validation.
Ensure scalability to support multiple floors and increasing number of vehicles without performance degradation.
Ensure maintainability by following SOLID principles and clean architecture.
Ensure extensibility to allow adding new parking spot types, pricing strategies, and floors without modifying existing code.
Ensure loose coupling by programming to interfaces rather than concrete implementations.
Ensure data consistency and integrity using transactional (ACID-compliant) operations.
Ensure configurability so pricing rules and system parameters can be changed without code modification.
Ensure reliability and availability so the system remains operational under load.
Ensure data validation and security to prevent invalid ticket usage and unauthorized access.
Ensure testability to support unit and integration testing of components.