Speed and Substance
A hard SQL 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
- 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. Collapse each pipeline to one point: its average run duration paired with its average net 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 and run your SQL against a real database
- Answer the interviewer's follow-up questions, then get a hire or no-hire decision