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Meta·Data Scientist·Technical Phone Screen·Senior

Senior
Jul 2026

Summary

Meta DS interview focused entirely on a single multi-part case around Instagram shopping. The question was dense and covered market sizing, experiment design, and debugging all in one go, which felt like a lot to juggle in real time.

Questions Asked (3)

Q1

Estimate the annual revenue opportunity of launching a shopping feature on Instagram.

Pricing & MonetizationProduct Analytics & Metrics
Author's notes

I went TAM to adoption to take-rate, which felt right structurally, but I fumbled the take-rate number pretty badly.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the scope: which shopping feature (e.g., in-app checkout, product tags) and which market (e.g., US only or global). Then use a top-down approach: estimate Instagram's user base, filter to those who engage with shopping content, estimate conversion rates and average order value, and multiply to get annual revenue. Be explicit about assumptions and consider multiple scenarios (low, medium, high).

Pro tip: Anchor your estimate to known Meta metrics (e.g., Instagram's ~2B MAU) and benchmark against industry standards (e.g., e-commerce conversion rates ~2-3%). This shows you can leverage internal knowledge and external data to build credibility.

1. Clarify scope and assumptions

Ask clarifying questions to define the feature (e.g., native checkout vs. product tags) and target market. State any assumptions you make (e.g., global rollout, 10% of users engage).

2. Estimate addressable user base

Start with Instagram's monthly active users (e.g., 2B). Estimate the percentage who are active shoppers (e.g., 20%) and the percentage who would use the shopping feature (e.g., 10%).

3. Estimate conversion and transaction metrics

Assume a conversion rate from browsing to purchase (e.g., 2%) and an average order value (e.g., $50). Also consider purchase frequency (e.g., 2 times per year).

4. Calculate annual revenue

Multiply the number of active shoppers by conversion rate, average order value, and purchase frequency to get annual revenue. Present the calculation clearly.

5. Sanity check and scenarios

Validate the result against industry benchmarks (e.g., total e-commerce revenue). Provide a range (low, medium, high) based on different assumptions to show robustness.

Key Points to Mention

  • Instagram's user base and engagement metrics (e.g., 2B MAU, 500M daily active users)
  • E-commerce conversion rates (typically 1-3% for social commerce)
  • Average order value (AOV) for social commerce (e.g., $50-$100)
  • Purchase frequency (e.g., 1-3 times per year)
  • Take rate or commission if Instagram takes a cut (e.g., 5-10% of transaction value)
  • Potential cannibalization or incremental revenue considerations

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

Q2

Design an A/B test to measure the impact of the Instagram shopping feature on GMV. Include your randomization unit, primary and guardrail metrics, and how you'd approach sample size.

A/B Testing & ExperimentationProduct Analytics & Metrics
Author's notes

This is where I spent most of my time.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the goal: measure the causal impact of the Instagram shopping feature on GMV. Then outline the experiment design: randomization unit, metrics, sample size, and analysis plan. Emphasize trade-offs and practical considerations for a social commerce context.

Pro tip: Mention that you would randomize at the user level to avoid interference, but also consider cluster randomization if there are network effects. Also, highlight the importance of guardrail metrics like user engagement and ad revenue to ensure the feature doesn't cannibalize other parts of the app.

1. Define Hypothesis and Goal

State the hypothesis that the Instagram shopping feature increases GMV. Clarify the primary objective: measure the causal effect on GMV, and ensure it aligns with business goals.

2. Choose Randomization Unit

Decide on the randomization unit: user-level is ideal to avoid interference, but if network effects exist, consider cluster randomization (e.g., by geography or social graph clusters). Discuss trade-offs.

3. Select Metrics

Define primary metric: GMV per user. Include secondary metrics: conversion rate, average order value, and engagement with shopping features. Guardrail metrics: overall app engagement, ad revenue, user retention, and page load time.

4. Determine Sample Size

Calculate required sample size based on expected effect size, power (80%), significance level (5%), and variance in GMV. Consider using historical data or a pilot to estimate variance. Account for multiple testing if needed.

5. Analysis Plan and Validity Checks

Plan for A/A tests, novelty effects, and long-term holdout. Use appropriate statistical tests (e.g., t-test, CUPED for variance reduction). Check for SRM and ensure metrics are not skewed by outliers.

Key Points to Mention

  • Randomization unit: user-level vs. cluster randomization and trade-offs
  • Primary metric: GMV per user; guardrail metrics: engagement, ad revenue, retention
  • Sample size calculation: power, significance, effect size, variance
  • Potential network effects and interference
  • Novelty effect and long-term measurement
  • Use of CUPED or other variance reduction techniques

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

Q3

Partway through the experiment, the treatment group's conversion rate drops sharply. Walk through how you'd troubleshoot this.

Root Cause AnalysisA/B Testing & Experimentation
Author's notes

Favorite part of the question, weirdly.

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AI HintsAI Generated

Suggested Approach

Start by confirming the drop is real and not a data artifact, then systematically rule out instrumentation, sample ratio mismatch, and external factors before considering treatment effects. Structure your answer around a logical troubleshooting flow, emphasizing validation and root cause isolation.

Pro tip: Always check for Sample Ratio Mismatch (SRM) first—it's a common culprit in A/B tests and can invalidate results. Also, consider novelty or primacy effects, especially if the drop is temporary.

1. Validate the Data

Check data pipelines, logging, and metric definitions for errors or changes. Ensure the drop isn't due to missing data or a bug in the analysis.

2. Check Experiment Health

Verify Sample Ratio Mismatch (SRM) and randomization integrity. Look for any changes in traffic sources or user composition that could bias results.

3. Investigate External Factors

Rule out seasonality, holidays, marketing campaigns, or other external events that could affect the treatment group disproportionately.

4. Analyze Treatment Effects

Segment the data by user demographics, device, or behavior to see if the drop is concentrated in a subgroup. Check for novelty effects or implementation issues.

5. Decide on Next Steps

If the drop is valid and persistent, consider pausing the experiment, communicating with stakeholders, and planning a follow-up test to confirm findings.

Key Points to Mention

  • Sample Ratio Mismatch (SRM) and its implications
  • Data quality checks and pipeline validation
  • External validity threats like seasonality or concurrent events
  • Segmentation analysis to identify heterogeneous treatment effects
  • Novelty and primacy effects in A/B testing
  • Stakeholder communication and decision-making based on findings

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