What is this question about?
This product design interview question tests whether you understand the process of going from customer needs to product development. This process should involve defining who the customer is and what they want to accomplish; defining multiple use case scenarios in which the customer performs activities that are related to your product; and prioritizing what to build.
What is the interviewer looking for?
The interviewer is evaluating you on the following:
- Do you provide keen insights about the customer and their needs?
- Are you able to provide multiple and diverse use case scenarios?
- Is your answer structured and logical, or do you go off on a tangent?
- Do you go beyond generalities in your solutions and provide detailed descriptions?
- Can you provide ideas that no other candidate has mentioned?
- Are you confident and sound credible? Would engineers and product people follow your lead?
How to structure your answer?
One way to structure your answer is by using the CIRCLES Method™ by Lewis C. Lin. A detailed description of this method is in the book Decode and Conquer. This method is useful in helping you think and answer in an organized and exhaustive way. The steps of this method are:
C — Clarify. Ask clarifying questions to narrow the scope.
I — Identify the users/customers as personas like food lovers, soccer moms, etc.
R — Report on the user’s needs (use cases). A use case is an activity that a user would like to do relative to the product.
C — Cut through and prioritize the use cases based on some attributes (revenue, customer benefit, complexity).
L — List solutions.
E — Evaluate the tradeoffs of your solutions.
S — Summarize:
- State which solution you would recommend.
- Recap what the solution does and why it is beneficial.
- Explain why you prefer this solution.
How to quickly think of several use cases?
In a previous article, we described three methods that can help spark ideas for use cases. The methods are: the 5Ws, word associations, and SCAMPER. In this example, we will use the Word Associations method.
INTERVIEWEE: What is the goal that the business wants to achieve with the new product?
INTERVIEWER: To increase our product line and grow revenue.
INTERVIEWEE: Okay, I would like to start by talking about the type of users that buy Nest products, who they are and what things they would like to do that the current Nest line doesn’t offer yet. After describing some use cases, I will select a few that may help Nest grow additional revenue. Then, I will brainstorm some solutions and wrap up.
INTERVIEWER: Sounds good.
INTERVIEWEE: Typical buyers of the Nest products are:
- Families that are technology savvy and have mid to high disposable incomes, that can afford to buy home automation devices. Some families may have more than one home and they probably would like to use home automation devices for monitoring and managing the operation of their second home.
- Property management businesses that maintain buildings and want a way to monitor buildings remotely.
- Realtors that show houses or apartments that may want to monitor locations remotely.
- Hotels that may want to use home automation technology to let their guests control room environmental settings.
Some of the buyers are also users, for example household owners are buyers and users. But in the case of businesses, like a property management business, the user would probably be a paid caretaker.
Now that I have identified who the users are, I want to talk about use cases for a new product. Homeowners are more familiar to me than the other types of users; homeowners are a large target market for Nest, so I would like to focus on these users.
INTERVIEWEE: Okay, go ahead.
INTERVIEWER: Ok, may I have a minute to think about new use cases for this segment?
(The interviewee takes their notepad and starts drawing word associations related to home automation.)
INTERVIEWEE: Okay, these are the use cases I am thinking about:
- Water quality may be of concern for families, so they may want to monitor the water quality coming from the tap (Association: Safety — Water).
- If the house had a gas leak, people would want to be warned (Association: Safety — Gas).
- Air pollution is a big problem in some cities, so people might want to know what the air quality is outside and inside their home (Association: Safety — Air).
- If there is a baby in the house, parents may want to monitor their baby’s breathing to make sure they’re okay (Association: Safety — Baby).
- In some homes, it’s difficult to maintain safe humidity levels. Unsafe levels cause sickness and mold to grow. So people may want to detect humidity levels and have a way to ventilate certain areas automatically (Association: House — Closets).
- Homeowners may want a garage door to open automatically when they arrive (Association: House — Garage).
- In homes that have a humidity problem, closets can accumulate mold; so a way to detect mold would be useful by notifying users that they need to clean and ventilate their closets in order to protect their belongings from being damaged by mold (Association: House — Closets).
- Houses with solar panels save in energy utility costs. People might want to know how much energy they are harnessing as well as their cost savings (Association: House — Solar Panel).
- In earthquake prone areas like San Francisco, homeowners may want to know how much their house foundation moved during an earthquake (Association: House — Earthquake).
- People who forget to water their potted plants may want to be reminded when to water them (Association: House — Plants).
- Homeowners with swimming pools may want a system that alerts them that it is time to change the water or disinfect it (Association: House — Swimming Pool).
- People may want their home’s main door to open automatically when they arrive instead of using their keys (Association: House — Doors).
- People with pets may like a system that feeds their pets for them (Association: House — Pets).
- Some parents are concerned about how much TV their children watch, so parents may be interested in knowing how many hours the children are watching TV (Association: Things — TV).
- Some households may have an expensive piano and may want to control the humidity and ventilation around it (Association: Things — Piano).
Of all these use cases, I think the ones that will lead to solutions with more revenue potential are the ones that are more frequent, provide greater benefit to the user, and can leverage from existing Nest technology or partners. I think the water quality, humidity levels and automatic main door opening cases are the best candidates in this respect.
Many people are concerned about water quality. If homeowners could have a way to check it, I am sure they would do it frequently. Being able to monitor water quality would give people a peace of mind. Nest could leverage partnerships with house product manufacturers to build a solution. Humidity in households is a big issue. It can cause mold problems that could damage a house, so a way to notify and prevent these problems is of great benefit, but is perhaps of a lesser concern than the water quality issue.
And, the automatic unlocking and opening of the front door could be a very convenient solution for some users, especially users who do not like to carry keys or users who have their hands full, such as carrying groceries, children, etc. This is a very frequent scenario, for which Nest could leverage its machine learning technologies to develop a face recognition-based solution. Therefore, of these three use cases, I think the automatic opening of the front door is the best one with respect to frequency, user benefit and technology leverage.
INTERVIEWER: Can you think of solutions to support this use case?
INTERVIEWEE: Sure. A wireless Nest camera could be installed as a door viewer. The door handle latch mechanism would be controlled electronically by the Nest system, which would open the door when it recognizes people that are authorized to go in. Neural network algorithms can be used to train a program to recognize people are allowed to go in the house. The training could be done by providing multiple photos of the people at different angles, which could be easily done through a mobile phone or the Nest camera itself. Unlike other Nest products, this one would require replacing the door’s lock with an electronic one that would require connecting it to a power source. People may be resistant to modifying the lock thinking they would need a professional to install it. But if the installation is made super easy in a DIY style, I think this product could be very popular.
One drawback is that in case of malfunction or loss of electric power the user would be locked out. This could be solved by leaving the regular key lock in place and change the internal latch mechanism to work with both the key and the electric Nest lock system.
To summarize, I explored multiple use cases and picked three that have the best attributes for building a new product: high frequency of use, provide benefit to the user in terms of convenience or notifications to take action, and a solution for which Nest could leverage its current technologies. Of the three use cases, the one that automatically opens the front door to home owners seems to me the best along these attributes. The solution I propose would leverage the Nest camera and Nest’s expertise in machine learning technologies. Its only drawback is that, it would require modifications in the door’s lock mechanism, but if the installation of the lock is designed to be a DIY solution, I think homeowners would be willing to try it, especially those of us who don’t like to carry keys.