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Shopify·Data Scientist·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Shopify data scientist interview with a coding question built around a real product scenario. Pretty applied, which I appreciated, though the threshold justification part tripped me up more than the code itself.

Questions Asked (1)

Q1

Write Python to compute a Jaccard similarity score between two lists, then use it to flag which custom themes are likely pirated by comparing them against a list of known pirate themes. Explain your threshold choice.

Algorithms & Data StructuresProduct Analytics & MetricsTechnical Trade-offs
Author's notes

The coding part was fine.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the data representation: are themes lists of tokens (e.g., color names, keywords) or sets? Then implement Jaccard similarity as intersection over union, and apply a threshold to flag likely pirated themes. Explain that the threshold should be chosen based on business trade-offs between false positives and false negatives, ideally validated with labeled data or domain knowledge.

Pro tip: Mention that Jaccard similarity is sensitive to list length and tokenization; consider normalizing or using weighted Jaccard if themes have varying sizes. Also, propose a data-driven threshold selection using precision-recall curves if labels are available.

1. Clarify requirements and data

Ask clarifying questions about the format of themes (lists of strings, sets, etc.), whether order matters, and what 'pirated' means in this context. Confirm the output: a flag per custom theme.

2. Implement Jaccard similarity

Write a Python function that takes two lists, converts them to sets, and returns the size of intersection divided by size of union. Handle edge cases like empty lists.

3. Compare and flag

For each custom theme, compute similarity against all known pirate themes, take the maximum similarity, and flag if it exceeds a threshold. Return a list of flags or a DataFrame with scores.

4. Choose and justify threshold

Select a threshold (e.g., 0.7) based on business impact: higher threshold reduces false positives but may miss subtle piracy. Discuss using labeled data to optimize via F1-score or precision-recall trade-off.

5. Discuss limitations and alternatives

Acknowledge that Jaccard ignores frequency and order; suggest alternatives like cosine similarity on TF-IDF or weighted Jaccard if needed. Mention scalability for large lists.

Key Points to Mention

  • Definition of Jaccard similarity: |A ∩ B| / |A ∪ B|
  • Edge cases: empty lists, duplicates (sets handle duplicates)
  • Threshold selection based on precision-recall trade-off and business costs
  • Use of maximum similarity across known pirate themes
  • Limitations: ignores frequency, order, and semantic meaning
  • Potential improvements: weighted Jaccard, cosine similarity, or token-based approaches

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