More reading: How to Implement A Recommendation System? (Stack Overflow)
A lot of machine learning interview questions of this type will involve implementation of machine learning models to a company’s problems. You’ll have to research the company and its industry in-depth, especially the revenue drivers the company has, and the types of users the company takes on in the context of the industry it’s in.
Source: Springboard

 
 
Answer from Analytics Vidhya:
‘People who bought this, also bought…’ recommendations seen on amazon is a result of which algorithm?
Answer: The basic idea for this kind of recommendation engine comes from collaborative filtering.
Collaborative Filtering algorithm considers “User Behavior” for recommending items. They exploit behavior of other users and items in terms of transaction history, ratings, selection and purchase information. Other users behaviour and preferences over the items are used to recommend items to the new users. In this case, features of the items are not known.
Know more: Recommender System