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Notion·Data Scientist·Take-home Assignment·Intermediate

Intermediate
May 2026

Summary

SQL take-home for a DS role at Notion, three questions around a doc collaboration dataset. Pretty clean problem set, nothing crazy algorithmic, but the collaboration rate definition question had more nuance than I expected.

Questions Asked (3)

Q1

Given a table of document access events, compute the distribution of how collaborators ended up on documents, including counts and percentages.

Product Analytics & MetricsData Modeling
Author's notes

Seemed straightforward until I had to decide whether to count unique users globally or unique (page, user) pairs.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the schema of the document access events table, especially how 'collaborator' and 'how they ended up on documents' are defined. Then write a SQL query that groups by the acquisition channel (e.g., invited, shared link, duplicate, template) and computes counts and percentages. Finally, validate the results and discuss potential edge cases or data quality issues.

Pro tip: Always clarify ambiguous terms like 'collaborator' and 'ended up on documents' before diving into SQL—this shows you think like a product analyst who cares about definitions and data quality. Also, mention that percentages should sum to 100% and consider using window functions for efficiency.

1. Clarify definitions and schema

Ask clarifying questions about the table structure, what constitutes a 'collaborator', and the possible values for 'how they ended up on documents' (e.g., invited, shared link, duplicate, template).

2. Identify the relevant columns and filters

Determine which columns to use for grouping (e.g., acquisition_channel) and any necessary filters (e.g., exclude deleted documents or inactive users).

3. Write the aggregation query

Use GROUP BY on the acquisition channel to count distinct collaborators per channel, then compute percentages using window functions or subqueries.

4. Validate and interpret results

Check that percentages sum to 100%, handle NULLs or 'other' categories, and discuss what the distribution implies for product decisions.

Key Points to Mention

  • Use COUNT(DISTINCT collaborator_id) to avoid double-counting if a collaborator appears multiple times.
  • Compute percentages with SUM(count) OVER () or a subquery to get the total.
  • Consider time-based filters (e.g., last 30 days) to focus on recent behavior.
  • Handle NULL or unknown acquisition channels by grouping them as 'Other' or excluding them.
  • Mention that the distribution can inform growth strategies, such as promoting high-performing channels.
  • Discuss potential data quality issues, like duplicate events or missing collaborator IDs.

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

Q2

For a given input user ID, find the other user they have collaborated with the most, where collaboration means both users appear on the same document page.

Data ModelingAlgorithms & Data Structures
Author's notes

Self-join on page_id after deduping, then group and count.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the data model: a many-to-many relationship between users and document pages. Then, for the given user ID, find all pages they appear on, identify all other users on those pages, and count co-occurrences to find the user with the highest count. Discuss efficient algorithms and data structures to handle large-scale data.

Pro tip: Mention that you would precompute collaboration counts offline using a batch job (e.g., MapReduce or Spark) to enable fast lookups, and consider edge cases like ties or no collaborators.

1. Clarify the data model and requirements

Confirm the schema: users, pages, and a mapping table (e.g., page_editors) linking users to pages. Ask about scale, update frequency, and whether the result should be real-time or can be precomputed.

2. Design a baseline algorithm

For a given user, retrieve all pages they are associated with, then for each page, retrieve all other users. Count occurrences of each collaborator and return the one with the maximum count.

3. Optimize for scale

Propose precomputing collaboration counts using a batch process (e.g., self-join on page_id, group by user pairs, count). Store results in a key-value store for fast retrieval. Discuss partitioning and indexing strategies.

4. Handle edge cases and ties

Define behavior when multiple users have the same maximum count (e.g., return any, or most recent). Handle cases where the user has no collaborators or appears on no pages.

5. Discuss trade-offs and extensions

Compare real-time vs. precomputed approaches. Mention potential extensions: weighting by page importance, time decay, or considering collaboration types (e.g., editing vs. commenting).

Key Points to Mention

  • Many-to-many relationship between users and pages
  • Self-join on page_id to generate user pairs
  • Group by user pair and count co-occurrences
  • Use of MapReduce/Spark for scalable precomputation
  • Indexing and partitioning for efficient lookups
  • Handling ties and edge cases (no collaborators, multiple max)

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

Q3

Which country has users who collaborate the most? Define a collaboration rate per country, justify your numerator and denominator, then compute it.

Product Analytics & MetricsData ModelingAdaptability & Ambiguity
Author's notes

This one actually made me think.

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AI HintsAI Generated

Suggested Approach

Start by defining collaboration as a meaningful user action (e.g., sharing, commenting, or editing together) and propose a rate like daily active collaborators per daily active users, segmented by country. Then discuss how to compute it using event data, ensuring to handle data quality issues and consider alternative definitions.

Pro tip: Acknowledge that collaboration can be defined in multiple ways and propose a primary metric while mentioning alternatives; this shows you understand the ambiguity and can make pragmatic choices.

1. Define Collaboration

Clarify what constitutes a collaborative action in Notion's context, such as sharing a page, commenting, or co-editing. Choose a definition that aligns with the product's core value.

2. Choose Numerator and Denominator

Select a numerator (e.g., number of users who performed at least one collaborative action) and denominator (e.g., total active users) for the rate. Justify why these capture collaboration intensity per country.

3. Data Collection and Segmentation

Identify the data sources (e.g., event logs, user profiles) and segment by country. Ensure you have reliable country attribution and sufficient data per country.

4. Compute and Compare

Calculate the collaboration rate for each country and rank them. Consider statistical significance and potential confounders like user base size or cultural differences.

5. Interpret and Validate

Interpret the results, check for anomalies, and validate with alternative definitions or time periods. Discuss limitations and next steps.

Key Points to Mention

  • Define collaboration clearly: distinguish between passive and active collaboration (e.g., viewing vs. editing).
  • Choose a rate that normalizes for country size: e.g., collaborators per active user, not absolute counts.
  • Consider time window: daily, weekly, or monthly active collaborators to capture engagement frequency.
  • Address data quality: ensure country data is accurate and handle missing or ambiguous geolocation.
  • Discuss potential confounders: e.g., team vs. individual usage, language, or product adoption stage.
  • Propose a validation method: e.g., compare with other engagement metrics or run a sensitivity analysis.

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