Design a Driver Earnings Tracker with Incremental Payment Processing

Mid May, 2026

Rippling

Mid-level

Early April, 2026

Rippling

Senior

Problem Overview: You are asked to design a system to track delivery drivers and compute their earnings. Initial APIs: addDriver(driverId, hourlyRate) recordTrip(driverId, startTime, endTime) getTotalCost() Details: Each driver has an hourly rate. Trips are defined by (startTime, endTime). Cost = duration * hourlyRate. Time precision is at least seconds, so you may need to convert to hours. Follow-up (this is where it gets interesting): The interviewer then extends the problem: payUpTo(time) Pay all completed trips up to a given timestamp getTotalPendingCost() Return remaining unpaid amount Key Challenges: This is NOT a typical DSA problem. It’s more like a mini backend system design implemented in code. Things that matter: Handling time intervals correctly Trips relative to payment cutoff Avoid double counting Incremental computation Avoid recomputing everything repeatedly Track what has already been paid Data modeling Drivers Trips Payment state Precision Converting seconds to hours Handling money (floating point vs exact values) Similar LeetCode Problems (closest analogies): This problem doesn’t map directly to a single LeetCode problem, but these are somewhat related: 981 Time Based Key-Value Store (querying state over time) 362 Design Hit Counter (time-window aggregation) 729 / 732. My Calendar I / III (interval handling) 146 LRU Cache (incremental state management)