How to crack Product design questions in PM interviews?

Product design questions are common in product manager interviews at firms like Google, Facebook or Amazon. For instance your interviewer might ask: "How would you design a phone for deaf people?"

This type of questions can really feel unsettling at first. But the good news is that if you know how to approach them they can become fairly easy to answer. So let's step through our recommended approach as well as a few examples to help you prepare for your interview.


1. How to answer product design questions

We recommend using a 3-step approach to answer product design questions in a product manager interview. This approach is also known as the BUS framework:

    1. Business objective
    2. User problems
    3. Solutions

    If you're preparing for a product manager interview we strongly encourage you to learn that framework as it can also be used for product improvement questions (e.g. How would you improve YouTube?) Let's step through each of the three steps one by one.

    How to answer product design questions?

    Step 1: Business objective

    Many candidates skip this step and start listing design ideas in an unstructured way. This is a big red flag for interviewers. Here are the things you need to do before starting to think about user problems and how to solve them:

    • Outline your answer
    • Define the business objective

    First, you should lay out your approach to solve the question. You could say something like this: "First, I'm going to try to understand the business situation and our objective in more details. Second, I will focus on defining the target user and brainstorming what problems we could solve for them. And third, I will generate solutions for these problems, prioritise them and make a recommendation."

    Outlining your answer shows you've got strong communication skills. If you jump straight in and answer the question in an unstructured way it will be very hard for your interviewer to keep up with you. They'll be thankful if you give them that overview.

    Second, you need to clarify the business situation and objective. Knowing the business context and what it's trying to achieve will help you make better design decisions later on. This is particularly important if the question your interviewer asks is vague.

    For instance, let's imagine your interviewer wants you to "Design a phone". Then you might want to ask what is the specific business objective we are trying to fullfill (e.g. sell as many phones as possible with a low price point, go for the premium market, etc.); and if we already have a user in mind for the phone (e.g. business users, teenagers, etc.). You'll design completely different phones depending on the answer to these questions.

    Step 2: User problems

    Now that you know more about the business situation and objectives it's time to think about the users and their problems in greater detail. Here are the things you need to do in that step:

    • Select a user type
    • List user problems
    • Prioritise user problems

    First, you should identify the different types of users for your product and you should select one to focus on. Let's go back to our phone example, and let's imagine your interviewer told you the business objective is to focus on a market that's particularly underserved. Here are some users you could suggest focusing on: deaf users, visually impaired users, elderly users, users with mobility issues, etc. You should list these different users and select one with your interviewer.

    Note that you can skip this part of the discussion if your interviewer has already specified a type of user they want to focus on in their initial question, or if you have already defined a user type with them in Step 1.

    It's also helpful to remember that for some products the user and the customer are not the same person. For example, that's the case for games that parents buy for their kids, or software (e.g. Jira) that managers buy for people to use in their teams.

    Second, once you've got a target user, you should think through what problems you can solve for them. An easy way to do this is to imagine your users using the existing product or service you're trying to replace.

    For instance, let's imagine we are focusing on deaf users. What are the problems they are facing with current phones? Here are some examples: 1) can't hear the phone ringing, 2) can't hear the other person talking on the line, 3) can't listen to voicemails, 4) can't hear app notifications, 5) can't hear the sound on videos received from friends, etc.

    Third, you should prioritise 1 to 3 items from the list of problems you have created. It's common to prioritise based on how painful that problem is for the user. For instance here, you could say something like: "My suggestion is to focus on solving problems 1) and 2) because those are the two features that really define a phone and they are currently inaccessible to deaf people."

    Step 3: Solutions

    Once you've defined the user problems you are trying to solve it's time to generate some solutions. Here's how to do it:

    • List solutions
    • Prioritise solutions
    • Summarise

    First, for each of the user problems you have identified you should generate potential solutions. Let's do this for user problem 1) deaf users can't hear their phone ringing. You could build a phone that does any of the following things when ringing: a) rings louder and for longer than standard phones to give more time to pick up, b) flashes bright colors on the screen, c) vibrates really strongly, d) is connected to a vibrating wristband / watch, e) sends visual notifications to other connected devices such as laptops, TVs, connected light bulbs, etc.

    At this stage it's helpful to draw a table with two columns on a piece of paper or whiteboard. The first column should contain the user problems you have decided to focus on. And the second problem should contain solutions to solve each problem.

    Second, once you've generated a few ideas it's time to prioritise the ones you will recommend building. A common way of doing this is to grade each solution from 1 (low) to 3 (high) based on how much value they would deliver for the user, and how easy they are to implement.

    The ratings you'll give will obviously be debatable as they will be based on judgement. But your interviewer is mainly interested in how you think, not the ratings themselves. So as long as you justify your grading with sound logic they will think you are doing a good job.

    After doing this you could tell your interviewer something like this: "After grading each solution, it looks like creating a simple wristband that vibrates when the phone rings is the simplest solution to implement to fully solve problem 1). Some other solutions are simpler to implement but only partially solve the problem." In addition, you would also need to do this for the other user problems you have selected in Step 2.

    After you have selected a few solutions it's also a good idea to talk about tradeoffs. For instance one trade-off regarding the wristband idea is that while it's effective at solving the problem it's an additional gadget the user needs to buy which might make it less attractive to some.

    Finally, after going through that exercise, it's a great idea to state the initial question again, and summarise what product you suggest building and why. This summary is a simple way of telling your interviewer that you are done answering the question. And again, it's an efficient way of showing you've got great communication skills.

    Mistakes to avoid

    There are two common mistakes candidates make when answering product questions that you can easily avoid.

    First, a lot of candidates simply skip the first step and start answering the question without agreeing a clear objective or target users with their interviewer. As mentioned above, this is a red flag.

    Second, many candidates don't spend enough time selecting a single target user and creating a short list of user problems. In other words, they start working on Step 3 too soon. The more work you do in Steps 1 and 2, the easier brainstorming and selecting solutions will become.

    2. Examples - Design a computer keyboard

    Now that you know what approach to use to answer product design questions let's apply it to a full example.

    Try answering the question below following the BUS method we have described. Play both the role of the interviewer and candidate, and make decisions regarding what business objective and target user to focus on. Leave a comment at the bottom of the blog post with your answer. We will reply to every question in the comment section.

    The key is to answer the question without seeing other people’s answers. To do so, scroll down directly to the bottom and leave your answer before reading other candidates’ proposals.

    Try this question:
    Design a computer keyboard
    Answer:

    You will find our proposed answer to the question below. Before taking a look at it, make sure you go to the bottom of the page and answer the question by yourself in the comments section. There are only so many opportunities to prepare for product design questions!

    1. Business objective

    Let's start by outlining the approach we are going to take. First, we will discuss the business objective. Second, we will analyse users and the problems we could solve for them. And third, we will look into solutions and make a recommendation.

    Here are the questions that immediately come to mind to clarify the business objective for this design question:

    • What's the business objective? Maximise profits? Focus on an underserved niche?
    • Do we already have a target user in mind or is that something we should explore / discuss?
    • Keyboards are often paired with mouses. Do we just want to design a keyboard or also a mouse that goes with it?

    Let's assume here that the interviewer wants us to design a keyboard for gamers but isn't interested in the mouse. And that the business objective is to maximise revenues.

    2. User problems

    Now that the business objective is clearer, let's start thinking about users and user problems in more details.

    There are different types of gamers we could focus on. An easy way to segment them is to split the market between casual and professional gamers. Given we want to maximise revenues, it makes sense to focus on casual gamers as it's likely to be a much bigger market than the professional's segment.

    Let's now brainstorm typical problems casual gamers face when using standard computer keyboards:

    1. User can't perform at their best because keys are slow to respond, dust builds up under them over time and isn't easy to remove
    2. User can't easily create personalised shortcuts as the software available to customise the keyboard is rudimentary
    3. User has to replace keyboard frequently as keys that are repetitively used wear out / break (e.g. space, shift, etc)
    4. User is distracted by noisy keys on keyboard
    5. User can't easily turn the game volume up / down from the keyboard
    6. User can't see keyboard keys when playing in the dark
    7. User's wrists / hands hurt as keyboard is uncomfortable to use for long periods of time
    8. Etc.

      Let's now prioritise these problems by putting ourselves in the shoes of a gamer. Most gamers' primary objective is probably to win at the game they play. As a result it makes sense to prioritise solving problems which will help users significantly improve their performance. Let's therefore focus on problems 1 and 2 as these look like they are the ones which could make the user faster and better if solved.

      3. Solutions

      Let's generate solutions now that we have selected a type of user (casual gamers) and a set of user problems (1 and 2 above).

      Here are some solutions which could help solve problem 1:

        1. Build keys that don't need to be pressed as hard / deep for the user input to be registered (Simplicity = 3, Value = 3, Total = 6)
        2. Build keys which register user input quicker thanks to alternative technologies (e.g. magnetic keys, mechanical keys, etc.) (S = 1, V = 3, T = 4)
        3. Build keys that can easily be removed to clean the keyboard or that don't let dust settle under the key caps (S = 2, V =2, T = 4)

          Here are some solutions which could help solve problem 2:

            1. Create a software that let's users define different sets of shortcuts depending on what game they play (Simplicity = 2, Value = 3, Total = 5)
            2. Create a software that makes automated suggestions for shortcuts based on commonly used shortcuts by other players with similar keyboards (S = 1, Value = 2, Total = 3)
            3. Create a software that let's users adjust how hard / deep they need to press the keys for their input to be registered (S = 1, V = 3, T = 4)
            4. Add additional buttons to the keyboard that let users generate a combination or keystrokes (i.e. a "macro") in a single keystroke (S = 3, V = 3, T = 6)

              Now that we have generated some solutions, let's prioritise them based on how easy they are to implement and how much value they bring to the user. We've rated the solutions from 1 to 3 directly inline above. For technical simplicity we've given 1 to the hardest solutions to implement, and 3 to the easiest. For value delivered to the user, we've given 1 to the least valuable solutions and 3 to the most valuable. And we've then added up both numbers.

              For problem 1, it therefore looks like prioritising solution a) makes sense. One of the tradeoffs to bear in mind when implementing that solution is that we might make the keys so sensitive that the user might inadvertently press the wrong keys more often. We will therefore have to balance sensitivity and control of the keyboard.

              And for problem 2, solutions a) and d) are promising options. Here an important tradeoff is balancing customisation and complexity. We're targeting casual gamers so we want to give them a good level of customisation but not make installing and personalising the keyboard too complex and lengthy.

              Finally let's summarise. Our recommendation is to build a keyboard for casual gamers as this is most likely to maximise revenues. We're also recommending to build features that will help the user maximise their performance but are relatively simple to implement. Here are the three features to build:

              • Keys which are more sensitive than standard
              • Software that lets user create shortcuts
              • Additional buttons for "macro" shortcuts
              How did you do? 

              Did you get to a similar answer? Leave a comment below with your thoughts and questions and we will answer them promptly. 

              3. List of practice design questions

              In addition, here are also a few more product design questions that were asked in PM interviews at Google and Facebook according to data from Glassdoor.com. If you have any questions about them or would like feedback on how to answer them you can leave your answer for one of the questions below and our team will get back to you.

                • Design a pen for an astronaut
                • Design an umbrella for kids
                • Design a phone for deaf people
                • Design a car for blind people
                • Design a dictionnary lookup for scrabble
                • Design an app for a community of Celiac's disease patients
                • Design a grocery app
                • Design a washer and dryer
                • Design an app for the Department of Motor Vehicles (DMV)
                • Design a bike-based delivery service
                • Design an elevator
                • Design an alarm clock
                • Design a new computer keyboard
                • Design Google radio
                • Design Google search
                Any questions about PM interviews?

                If you have any questions about product management interviews, do not hesitate to ask them below and we will be more than happy to answer them. All questions are good questions, so go ahead!

                Keep reading: product manager interview articles