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The Payload Flattener

A medium Python mock interview question on DataDriven. Practice with AI-powered feedback, real code execution, and a hire/no-hire decision.

Domain
Python
Difficulty
medium
Seniority
junior, mid, senior

Interview Prompt

Our product catalog API returns deeply nested JSON, but the warehouse expects flat rows with no nesting. Write a function that takes a nested dictionary and produces a flat one where keys from different levels are joined with a separator. No libraries allowed.

How This Interview Works

  1. Read the vague prompt (just like a real interview)
  2. Ask clarifying questions to the AI interviewer
  3. Write your python solution with real code execution
  4. Get instant feedback and a hire/no-hire decision