Product Designer interview question
How do you present a design portfolio case study?
Present the problem, users, constraints and your role; show research evidence, alternatives and decision rationale, collaboration and iteration, the shipped outcome and measurable impact, plus what you would change—not only polished screens.
Direct answer
What a strong answer covers
How it works
A case study is an argument that you make good decisions, not a gallery of screens. It opens with the problem, who had it, the constraints, and what your role was versus the team’s. It shows the research that shaped the direction and the alternatives you considered, with the reason each was dropped. The iterations demonstrate how feedback changed the design. The outcome is what shipped and what it changed, in numbers where possible, and the closing reflection names what you would do differently, which signals judgement more than any polished mock-up. The reader should finish knowing how you think.
Example
A case study for a checkout redesign opened with a 34 percent cart abandonment rate on mobile and a constraint of no backend changes for two quarters; it showed five observed sessions, three layout directions with the reasons two were dropped, two rounds of usability testing that changed the address form, the shipped flow, a drop in abandonment to 26 percent over eight weeks, and a note that the designer would have pushed for address autocomplete earlier despite the backend constraint.
Common mistakes
- Showing final screens with no problem, alternatives, or outcome.
- Claiming the whole team’s work as yours.
- Ending with success and no reflection on what you learned.
A useful answer structure
Answer from your own work.
Do not memorise a script: use only examples you can explain honestly in follow-up questions.
Open the desktop workspace and rehearse a clear answer in your own words.