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Free on the App Store

Quarry

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

View on the App StorePrivacy policy

Version 1.1 is free for iPhone and iPad. It is designed for iPhone Duo. The fold-aware layout needs iOS 27.1 or later. The app itself runs on iOS 18 or later.

Quarry: SQL & Data Interview

On the App Store

  • iPhone
  • iPad
  • iPhone Duo
Features

What you can practice

Quarry is free, with no in-app purchases and no ads. It is built for analysts, data engineers, data scientists and software engineers.

168 problems

61 SQL, 22 pandas and 85 Python problems, covering algorithms and data structures. Easy 55, Medium 90, Hard 23. Version 1.1 adds 60 problems (48 SQL and 12 pandas), including a 30-problem staff-level data engineering set with no company tag: gaps and islands, sessionisation, slowly changing dimensions, funnels and retention. The other 30 new SQL problems are company-style sets.

Graded on your device

Your output is checked against the expected result, with no self-marking. You get instant correct or incorrect feedback, and you can see the query plan for your SQL.

Practice in the style of a company

Filter problems by the company you are interviewing at. Each one is an original practice problem written in that company's style. They are not official questions, and Quarry is not endorsed by or affiliated with any of these companies. 137 problems use 'In the style of'. One problem is labelled 'Reported at Meta' because it matches publicly reported interview topics. It is still not an official question.

Hints, solutions and a Playground

Hints and full solutions sit with each problem. Difficulty runs from Easy to Hard, grouped by topic. The Playground is a free-form scratch space for SQL and Python.

Designed for iPhone Duo

On iPhone Duo, the question and editor sit side by side when the phone is open, and the layout focuses when it is closed. It adapts as you fold. The fold-aware layout needs iOS 27.1 or later. The app itself runs on iOS 18 or later, with a native design for iPhone and iPad in light and dark mode.

Private by design

Quarry has no accounts, no analytics, no ads and no tracking. It collects nothing, and practice works fully offline. There are no third-party analytics, advertising, crash-reporting or tracking SDKs.

Screenshots

Version 1.1 on iPhone

  • A solved Quarry SQL problem, with a correct result and the rows that were checked.
  • A Quarry SQL question and editor, with an 'In the style of' company chip.
  • The Quarry problem list, filtered by topic and difficulty.
  • The Quarry home screen, with progress by track.
  • The Quarry Playground, with SQL and Python scratch files.

Screenshots from the App Store listing for version 1.1. Company names show the style a problem is written in. They are not official questions from that company, and they are not endorsed by or affiliated with it. Company names belong to their owners and appear only to describe the style of a practice problem.

Version 1.1

What's new

Version 1.1 includes:

  • Designed for iPhone Duo: question and code side by side, adapts as you fold
  • 60 new problems, including a staff-level data engineering set
  • New native design with light and dark mode
  • Clearer results with instant correct or incorrect feedback
  • See the query plan for your SQL
  • Bug fixes and performance improvements
Details

At a glance

Price
Free. No in-app purchases and no ads.
Version
1.1
Category
Education. Also listed under Developer Tools.
Language
English
Age
4+
Size
134.1 MB
Seller
Mayank Gulaty. © 2026 Flowbit Studio.
Devices
iPhone and iPad. Requires iOS 18.0 or later on iPhone, and iPadOS 18.0 or later on iPad. The fold-aware iPhone Duo layout needs iOS 27.1 or later. On Mac it is the iPad app (Apple silicon, macOS 15 or later), designed for iPad and not verified for macOS. On Apple Vision it is the iPad app (visionOS 2.0 or later). Those are iPad-app compatibility modes.
Released
23 October 2026.
Support

Help with Quarry

Contact: mayank@flowbitstudio.ie. Quarry is developed by Mayank Gulaty in Dublin. There is no phone number.

mayank@flowbitstudio.iePrivacy policy

Does Quarry need an internet connection?

No. Quarry practice works offline. The Support and Privacy links in Settings open web pages, which need a connection.

How do I restore my progress?

Progress and drafts stay on the device. They are not stored in an account, so they do not transfer to a new phone.

Are the company problems official?

No. They are original practice problems written in the style of a company, such as Amazon or Google. They are not official questions, and Quarry is not endorsed by or affiliated with those companies. One problem is labelled 'Reported at Meta' because it matches publicly reported interview topics; it is still not an official question.

Do you collect any data?

No. Quarry collects nothing. There are no accounts, no analytics, no ads and no tracking, and practice works fully offline. The privacy policy is on this site.