Speed and Substance

A hard SQL interview practice problem on DataDriven. Write and execute real sql code with instant feedback.

Domain

SQL

Difficulty

hard

Seniority

L5

Problem

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?

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