I had a one-hour phone interview conducted in two separate, half-hour calls.

The first call was with the hiring manager. He explained that the team primarily focuses on data mining and asked about my real-world experience in this area. This led to a discussion about Amazon's recommendation system, and he then asked how I would design such a system. The conversation was polite and pleasant.

The second call was with a senior engineer on the team. He inquired about my experience and the skills required for the position. We encountered a challenge in our discussion; I often had difficulty understanding his questions. He refined his questions several times, and ultimately, we both worked hard to define the problem. Overall, he seemed like a nice person.

I informed the manager that I wouldn't be available soon. This, perhaps along with other factors, may have led to no further progress.

How would you design a recommendation system (like Amazon)?