Three Hours for Yesterday's Numbers
A medium Spark mock interview question on DataDriven. Practice with AI-powered feedback, real code execution, and a hire/no-hire decision.
- Domain
- Spark
- Difficulty
- medium
- Seniority
- L5
Interview Prompt
A nightly job refreshes `daily_category_sales`, a summary of one day's sales broken down by product category, but it rebuilds from the entire multi-year `transactions` history on every run even though only the most recent day is ever new. For the latest day present in `transactions`, total each product category's revenue and units sold, and make the job read only that day's data rather than the whole table.
Summary
Three terabytes scanned. One day changed.
How This Interview Works
- Read the vague prompt (just like a real interview)
- Ask clarifying questions to the AI interviewer
- Write your spark solution with real code execution
- Get instant feedback and a hire/no-hire decision