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Shopify·Data Scientist·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Shopify data scientist interview with a SQL-heavy analytical question about merchant behavior. One question, but it had enough layers to trip you up if you weren't thinking carefully about the denominator.

Questions Asked (1)

Q1

Given tables for merchants, themes, and theme installations, write a SQL query that shows, for each calendar year, what percentage of active merchants installed at least one pirated theme. Then interpret whether piracy adoption is growing year-over-year.

Product Analytics & MetricsData Modeling
Author's notes

The join logic isn't the hard part.

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AI HintsAI Generated

Suggested Approach

First, clarify the schema and definitions (e.g., active merchants, pirated themes, installation date). Then write a SQL query that joins merchants, theme installations, and themes, filters for pirated themes, and computes the percentage of active merchants per year who installed at least one pirated theme. Finally, interpret the year-over-year trend to assess growth in piracy adoption.

Pro tip: Always state your assumptions about ambiguous terms like 'active merchant' and 'pirated theme' upfront, and consider using window functions or CTEs for clarity and performance.

1. Clarify Definitions and Schema

Confirm what 'active merchant' means (e.g., merchants with at least one sale in the year) and how 'pirated theme' is identified (e.g., a flag in the themes table). Also, understand the grain of the theme_installations table.

2. Identify Active Merchants per Year

Create a CTE that lists distinct merchant IDs active in each calendar year, based on the definition of active (e.g., from a sales or activity table).

3. Find Merchants with Pirated Theme Installations

Join theme_installations with themes to filter installations of pirated themes, then extract distinct merchant IDs and the year of installation (or year of activity if installation date is not available).

4. Compute Percentage per Year

For each year, count the number of active merchants and the number of those who installed at least one pirated theme. Calculate the percentage as (count of pirates / count of active merchants) * 100.

5. Interpret Year-over-Year Trend

Compare the percentages across years to determine if piracy adoption is growing. Consider statistical significance and potential confounders (e.g., changes in merchant base or detection methods).

Key Points to Mention

  • Definition of 'active merchant' and how it impacts the denominator.
  • Identification of pirated themes (e.g., flag in themes table).
  • Handling of merchants with multiple installations (use DISTINCT to avoid double-counting).
  • Time frame alignment: ensure installation year matches active year.
  • Use of CTEs or subqueries for readability and performance.
  • Interpretation should consider absolute numbers and potential biases.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.