One Door Each
A medium Data Modeling mock interview question on DataDriven, with an AI interviewer who asks follow-up questions and a hire or no-hire decision at the end.
- Domain
- Data Modeling
- Difficulty
- medium
- Seniority
- L5
Interview Prompt
We run dozens of product experiments at once on our consumer app, and each user who enters an experiment is locked to a single variant for its duration: either the control or one of the treatment groups. Analysts measure lift by joining each user's variant assignment onto our existing event log, which stays untouched, and counting only the events that occurred after the moment that user was enrolled. Design the data model so a user can never land in two variants of the same experiment, and so an analyst rolling metrics up by variant can tell the control apart from the treatment groups.
Summary
Every user picks a lane and stays in it. Model the world so the numbers stay honest.
How This Interview Works
- Read the vague prompt (just like a real interview)
- Ask clarifying questions to the AI interviewer
- Draw your data model on the schema canvas: tables, keys and relationships
- Answer the interviewer's follow-up questions, then get a hire or no-hire decision