Rippling - SSE - Rejected

I recently interviewed for a Staff Software Engineer (SSE) position at Rippling. My interview consisted of one Data Structures & Algorithms (DSA) round, which was conducted via a Hackerrank codepair link. The round started with brief introductions from both my interviewer and myself.

The primary task was to implement three APIs for a delivery system application. The core requirement was that a delivery driver has an hourly rate for performing deliveries. I was asked to implement the following three APIs:

• addDriver(driverId: integer, hourlyRate: float)
• addOrder(driverId, startTime, endTime): I also had to mention my choice of data type for time and justify it.
• getTotalCost() for all the deliveries.

I found the initial question straightforward.

There were also follow-up questions:

• "What is the issue with using float and double as data types for currency, and what data type should you use instead?"
• "What changes would you make in the code if we wanted to update the hourly rate of a driver?"

I felt optimistic about this round because I was able to write production-level code, handling concurrency and other best practices, and I answered all the follow-up questions effectively.

Despite my performance, I was ultimately rejected. The recruiter mentioned that I had only solved one out of the three required questions. They stated that for the other two questions, at least the approach needed to be discussed. I had specifically asked the interviewer about the time limit and the number of questions at the beginning. The interviewer responded casually, advising me to proceed at my normal speed and ensure the code was production-level. I believe that if the interviewer had set clearer expectations, I would have planned my execution strategy differently.