Quarry: SQL & Data Interview

Data interview practice that runs entirely on your device. Write real SQL and Python (pandas), get graded instantly, and see exactly why.

NEW IN 1.1
• Designed for iPhone Duo: question and editor side by side when open, a focused layout when closed, and it adapts as you fold.
• A new native design for iPhone and iPad, in light and dark mode.
• 60 new problems: a staff-level data engineering set (gaps and islands, sessionisation, slowly changing dimensions, funnels, retention) and company-style SQL sets.
• Clearer results: instant correct / not quite feedback, expected vs. actual tables, and the query plan for your SQL.

WHAT'S INSIDE
• 168 problems across three tracks: 61 SQL, 22 pandas and 85 Python (algorithms and data structures).
• Real execution, real grading. Your output is checked against the expected result, with no self-marking.
• Company-style practice. Filter problems written in the style of the company you're interviewing at.
• Hints and full solutions when you're stuck.
• Difficulty levels from Easy to Hard, grouped by topic.
• A free-form Playground for scratch SQL and Python.

PRIVATE BY DESIGN
No accounts. No analytics. No ads. No tracking. Quarry collects nothing and works fully offline.

Built by a working data engineer, for analysts, data engineers, data scientists and software engineers who want a quiet, fast place to actually practice.