Food-Delivery Driver Payments System

Context

You are designing a small, object-oriented component to track and pay food-delivery drivers based on their hourly rate and completed delivery durations. Deliveries are recorded only after completion and never exceed 3 hours.

Assume all times are UTC and recorded with at least 1-second precision using Unix epoch time.

Requirements

Implement an object-oriented API with the following methods:

1. add_driver(driver_id, usd_hourly_rate)
   • Registers a driver and their current hourly rate in USD.
2. record_delivery(driver_id, start_time, end_time)
   • Records a completed delivery for the driver.
   • Time format must support ≥1-second precision.
   • Each delivery duration ≤ 3 hours.
   • Deliveries are recorded only after completion (end_time ≤ now).
3. get_total_cost()
   • Returns the total cost of all deliveries (paid and unpaid).

Then extend the system with:

4. pay_up_to(pay_time)
   • Marks deliveries as paid if their end_time ≤ pay_time (Unix epoch time).
5. get_total_cost_unpaid()
   • Returns the total cost of all unpaid deliveries.

Discussion Prompts

• Storage choices (in-memory vs. persistent), data modeling, and indexing.
• Assumptions (time zone, precision, rate changes, rounding).
• OOP practices (entities, services, repositories, immutability, interfaces).
• Any sensible deviations from production for an interview-quality solution.