Speed and Substance
A hard SQL mock interview question on DataDriven. Practice with AI-powered feedback, real code execution, and a hire/no-hire decision.
- Domain
- SQL
- Difficulty
- hard
- Seniority
- L5
Interview Prompt
We're building an observability view over pipeline runs and want a single figure for how tightly a pipeline's speed tracks its throughput. Counting only the runs that logged both a duration and their row counts, collapse each pipeline to one point: its average run duration paired with its average net row output, where a run's net output is `rows_out` minus 10 percent of `rows_in`. There's no correlation function to lean on here, so compute the Pearson correlation between those two per-pipeline figures straight from its definition.
Summary
When a run takes longer, is it moving more rows or just stalling?
How This Interview Works
- Read the vague prompt (just like a real interview)
- Ask clarifying questions to the AI interviewer
- Write your sql solution with real code execution
- Get instant feedback and a hire/no-hire decision