Got asked this question from a LA based start up. I managed to do something (mostly got thrown off because was expecting Leetcode style questions) but dont think the inteviewer was satisfied. Can Someone help me with how to better approach these questions

The requirements were pretty vague, here is what my inteviewer told me
The exercise is very open-ended and meant to understand your process in designing something "new".
Scenario: imagine your team is giving you this task of creating a small microservices (the one in the doc); how would you proceed?

Ideally, you could start with a paragraph gathering requirements/user stories, one for the overall design, one for the technical implementation from storage to API, and finally, some success criteria or test cases.
Code isn't necessary, but if it helps, either pseudocode or actual code works :)