Product Manager Interviews Module 2 – Product sense and product design
Designing a product for a user group
Answer design-a-product questions end to end: choose a user and a problem, compare three solutions, decide with criteria and define an MVP with its metrics.
What you will learn
- Answer a design-a-product question end to end with the six-step method
- Generate distinct solutions and choose one with explicit criteria
- Define a minimum viable product and say what it leaves out
- Name the success metrics and guardrails of the product you design
Before you start
What you’ll learn · Before you start
What you will learn
- Answer a design-a-product question end to end with the six-step method
- Generate distinct solutions and choose one with explicit criteria
- Define a minimum viable product and say what it leaves out
- Name the success metrics and guardrails of the product you design
Before you start
On this page
Design a product for people who have just moved to a city and need home repairs they can trust. The prompt names a group of people and a need and leaves the rest to you: no product, no data and about 45 minutes in which to reach one decision the interviewer can follow.
Below, that prompt is answered end to end at the depth of a solid mid-level answer, with the track’s six steps: a user, a problem, three solutions, a decision with criteria, the smallest first version and the numbers that would show it worked.
One prompt, six steps, one decision
Design questions take the shape “design a product for [a group of people] in [a situation]”. Nothing exists yet, which sets them apart from improving a product or critiquing one, so the user and the problem you choose carry the whole answer. Step through the home-repair prompt, answered with the six steps of the method lesson:
The drawing shows the whole scene; its 9 steps are listed below.
Every step as text
- The prompt. The prompt: design a product for people who have just moved to a city and need home repairs they can trust. The candidate has about 45 minutes and checks in after clarifying, after choosing the user and after deciding.
- Clarify. Two questions that change the plan: is this a new product or part of an existing app, and what does success mean? The interviewer says a new service in one large city, and the goal is people who come back. The candidate states one assumption aloud: success is a second booking.
- Choose a user. Three groups need repairs: owners of newly built flats, older people who live alone, and tenants who moved for a job in the last six months. The candidate picks the new tenants: they know nobody to ask, and a leak cannot wait for a slow landlord.
- Name the problem. Their problems: not knowing whom to let into their home, not knowing a fair price, and not being home when a worker is available. Trust comes first, because no other problem matters until they open the door.
- Three solutions. Three approaches, not three features: a directory of checked workers with reviews, a managed service that sends its own vetted workers at fixed prices, and a board where neighbours recommend workers they have used.
- Check a limit. One fact decides between the first two, so the candidate checks it: can the company employ and vet its own workers? The interviewer says yes. A company that only writes software would have to start from the directory.
- Decide. The criteria: the effect on trust, the effort, the risk and the fit with repeat use. The managed service wins on trust and fit, at the highest effort, an operations team. The board fails new tenants, who have no neighbours on it yet.
- First version, metrics. The first version tests the riskiest assumption, that new tenants will let a vetted stranger in at a fixed price: three common jobs, two neighbourhoods, ten workers, booked by phone. Success is the share of first customers who book again within 60 days, with damage or safety complaints as the guardrail.
- The answer, end to end. A new tenant in a strange city, a problem of trust, a managed service chosen from three with the criteria said aloud, a first version that tests one assumption, and a number that would show people came back.
Each step answered the question the next one needed. The new tenants made trust the problem, trust made the managed service the choice, and the choice decided what the first version had to test. Google’s interview tips ask candidates to tell the interviewer when they make an assumption or go deep instead of broad, and why. Choosing one group and one problem is going deep, so say why you chose them.
Not affiliated
Based on public information about Google and Atlassian. MySmartCoPilot is not affiliated with Google and Atlassian, and Google and Atlassian’s real interview advice may differ from what this lesson describes.
Three solutions that differ in approach, then a decision
Distinct solutions differ in how they solve the problem. A directory, a managed service and a neighbours’ board are three approaches; search, filters and reviews are three features of one directory. The Double Diamond, the Design Council’s picture of the design process, works the same way in its second half: develop different answers to the problem you defined, then test them on a small scale.
Then decide with criteria said aloud: the effect on the chosen problem, the effort, the risk and the fit with the goal. Atlassian’s product interview handbook lists prioritising for outcomes, and saying no when needed, among the skills it looks for. Answer the questions about the company, and the table marks the solutions that fit.
Answer the questions above: the table then marks what fits your case and says why the rest does not.
| Solution | Effect on trust | Effort | Risk | Fit with repeat use |
|---|---|---|---|---|
| Verified directory Approach: a tool: checked workers and their reviews | Mixed A checked badge helps, but reviews can be faked and new workers have none | Good Software and a check of each worker: a small team can build it | Mixed A bad job reflects on the app, which controls nothing after the booking | Mixed People may come back, but each job depends on workers it does not employ |
| Managed repair service Approach: a service: its own vetted workers at fixed prices | Good The company vets every worker, fixes the price first and stands behind the job | Poor Hiring, vetting, scheduling and support: an operations team before any app | Mixed Worker supply and liability for damage sit with the company | Good One good job makes the next booking likely, which is the goal |
| Neighbours' board Approach: a community of recommendations | Good People trust a neighbour who used the worker last month | Good A board and a check of who posts | Mixed Empty for weeks in an area where nobody has posted yet | Poor New tenants are the people least likely to know a neighbour to ask |
How the answers decide
- “What does the company want from its first year?” People it serves coming back: adds a caveat to Verified directory and Neighbours' board. Repeat use needs a good job every time. A directory controls nothing after the booking, and a new tenant has no neighbours on the board yet.
- “What does the company want from its first year?” As many users as fast as possible: adds a caveat to Managed repair service. A managed service grows only as fast as it can hire and vet workers, so it reaches people slowly.
- “Can the company employ and vet its own workers?” No, it only writes software: rules out Managed repair service. Without its own workers there is no managed service to offer. Start from the directory and make its checks as strict as software allows.
- “Must the first version launch within three months?” Yes: adds a caveat to Managed repair service. Hiring and vetting a first team of workers can fill most of three months before the first job is done.
In short: with repeat use as the goal and an operations team within reach, the managed service fits. A company that only writes software starts from the directory and accepts a weaker hold on trust.
Key idea
Generate approaches, not features, and decide with the criteria said before the choice, so that the interviewer can follow why one approach beat the other two.
Checkpoint
Check: Distinct solutions and a decision with criteria · The six steps on a design prompt
The first version tests the riskiest assumption
A minimum viable product: The smallest version of a product that real users can try, built to test whether the solution's riskiest assumption holds. It leaves out everything that the test does not need. is the smallest version that real users can try and that shows whether the solution’s riskiest assumption holds. For the managed service, that assumption is that new tenants will let a vetted stranger into their home at a price fixed in advance. If they will not, nothing else about the service matters, so the first version tests that and leaves the rest out:
| In the first version | Left out until the assumption holds |
|---|---|
| Three jobs: a leaking tap, a tripped switch, a jammed door | Every other trade |
| Two neighbourhoods where many tenants are new | The rest of the city |
| Ten vetted workers at fixed prices | Independent workers |
| Booking by phone or a short form | An app with payments and ratings |
Saying what the first version leaves out, and why, is what interviewers listen for: it shows that you know what the test needs.
A smaller copy of the whole product
Wrong: “Version one has every feature, with fewer screens.” Right: “Version one tests one assumption, that new tenants will let a vetted worker in.” A smaller copy of everything tests nothing in particular and takes almost as long to build.
Metrics follow the goal, with a guardrail
The goal was repeat use, so the primary metric is the share of first customers who book a second job within 60 days. Supporting metrics explain why it moves, and a guardrail metric: A metric that must not get worse while a team pushes another metric up, such as notification opt-outs while it sends more offers. If it does get worse, the change is stopped or rethought. More in “Product metrics and the north star metric” watches what the push could break:
| Metric | Its role |
|---|---|
| Second booking within 60 days, by first customers | Primary: the goal itself |
| Jobs fixed on the first visit | Supporting: a reason people return |
| Hours from request to visit | Supporting: a reason people return |
| Damage or safety complaints per 100 jobs | Guardrail: must not rise |
Give the primary metric a number to beat and say what a miss would mean. MySmartCoPilot’s example: if fewer than one first customer in four books again, trust is not there yet, and the next step is to ask the others why.
Checkpoint
Check: The minimum viable product · Metrics and a guardrail
Practise: first decisions for two briefs
Make the first decisions for two new briefs. Each choice says why it is right or what it misses.
Checkpoint
Your first decisions
The self-check that follows picks each next question from the idea you have answered least well so far.
Practice that adapts to you
Practise this lesson
12 questions about 7 ideas of this lesson. Each answer is explained at once, and what you get right is kept in this browser.
One prompt answered at three levels, with what each adds Pro: opens with a Pro, Premium or Ultimate pass
The same home-repair prompt, answered by an associate, a mid-level and a senior candidate. The six steps stay the same; each level looks further ahead, at risks, at the order of work and at the people needed to make it happen.
In this part:
- What the associate answer gets right, and where it stops
- What the mid-level answer adds: options, criteria and a test
- What the senior answer adds: order, risk and the economics
- A rubric for each level
1 diagram · about 5 minutes
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Five slips that cost the round, reproduced and fixed Pro: opens with a Pro, Premium or Ultimate pass
Weak design answers usually fail in one of five ways. Each slip below is shown as a candidate says it, then rewritten, with the follow-up an interviewer is likely to ask on hearing it.
In this part:
- Slip one: features before anyone is chosen
- Slip two: options listed but never chosen
- Slip three: success with no number to judge it by
- Slip four: a limit of the prompt ignored
- Slip five: ten ideas and no depth
- The five slips side by side
- Hearing a slip in your own answer, minute by minute
about 4 minutes
Opening this part with your pass…Pro part. It opens with the same pass as the part above.
Four practice briefs with scoring guides Pro: opens with a Pro, Premium or Ultimate pass
Four original briefs to answer aloud, 25 minutes each. Each has a scoring guide that says what a strong answer contains at each step, and a sample decision path to compare with yours afterwards, never before.
In this part:
- Brief 1: a clinic whose patients live 30 km away
- Brief 2: a college canteen at lunch hour
- Brief 3: a warehouse team on night shifts
- Brief 4: freelance designers looking for clients
about 4 minutes
Opening this part with your pass…Pro part. It opens with the same pass as the part above.
Interview questions
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Fresher to mid · Warm-up
What makes a product a minimum viable product, and what is it not?
A minimum viable product is the smallest version of a product that real people can use, built to test whether the solution's riskiest assumption holds. Minimum means that everything the test does not need is left out; viable means that what remains does the job well enough for people's behaviour to tell you something. For a service that lends tools between neighbours, the riskiest assumption might be that people will lend a drill to a stranger, and a first version could be a shared list for one apartment block, run by hand for a month. It is not a buggy copy of the full product, a demo that nobody uses or every planned feature with fewer screens, because none of those tests one assumption. In an answer, name the assumption, say what the first version leaves out and what result would change your plan.
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Fresher to senior
Design a product for working parents of toddlers in a large city. Walk through your user choice, the problem you solve and how you would know it worked.
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Mid to senior
Design a product that helps smallholder farmers decide when to irrigate. What do you build first, and which constraints change your design?
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Fresher to mid
Design a product for students living in college hostels. The interviewer wants the one feature you would launch first and its success metric.
Flashcards · 6 cards
Recall it, then check
Say the answer to yourself before you look: recalling it is what makes it stick.
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What sets a 'design a product' question apart from improving or critiquing one?
Nothing exists yet. The prompt names a group of people and a situation, so the user and the problem you choose carry the whole answer.
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What makes the solutions in a design answer distinct?
They differ in approach, not in features. A directory, a managed service and a neighbours' board are three approaches; search, filters and reviews are three features of one directory.
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Which criteria should you name before choosing between design solutions?
The effect on the chosen problem, the effort, the risk and the fit with the goal, said aloud before the choice, so the interviewer can follow why one approach beat the other two.
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What is a minimum viable product in a design answer?
The smallest version real users can try that shows whether the riskiest assumption holds. For a managed home-repair service that assumption is whether new tenants will let a vetted worker in at a fixed price, so version one offers three jobs in two neighbourhoods and leaves the rest out.
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Why is 'version one has every feature, with fewer screens' a weak first version?
A smaller copy of everything tests no assumption in particular and takes nearly as long to build. Name the one assumption the first version tests, and say what it leaves out and why.
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How do the metrics of a design answer fit together?
One primary metric tied to the goal, here first customers booking a second job within 60 days; supporting metrics that explain why it moves; and a guardrail that must not rise, such as damage complaints per 100 jobs. Give the primary metric a number to beat.
Key takeaways
- A design question starts from people and a need, so the user and the problem you choose carry the whole answer.
- Generate three approaches rather than three features, and choose with the criteria said first.
- The minimum viable product is the smallest version that tests the riskiest assumption; say what it leaves out.
- Tie one primary metric to the goal, explain it with supporting metrics and protect it with a guardrail.
Terms in this lesson
- minimum viable product
- The smallest version of a product that real users can try, built to test whether the solution's riskiest assumption holds. It leaves out everything that the test does not need.
References
- The Double Diamond (Design Council (CC BY 4.0))
- Atlassian product interview handbook (Atlassian)
- Interviewing at Google: best practices, advice and tips (Google Careers)
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