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DoorDash·Data Scientist·Technical Phone Screen·Senior

SeniorPrefer not to say
Jun 2026Remote

Summary

DoorDash data science case interview focused entirely on diagnosing a drop in successful orders for a food delivery marketplace. Heavy emphasis on structured thinking across demand, supply, and operational dimensions, plus experiment design. No behavioral questions from what I remember.

Questions Asked (4)

Q1

Successful orders in one geographic market have been declining for four weeks. What could be causing this?

Root Cause AnalysisProduct Analytics & Metrics
Author's notes

This is where I spent way too long listing possibilities without organizing them.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the metric definition and scope (e.g., successful orders = completed orders, geographic market = specific region, time frame = 4 weeks). Then systematically break down potential causes into internal (product, operations, marketing) and external (competition, seasonality, macro) factors, and outline how you would validate each with data.

Pro tip: Demonstrate a hypothesis-driven approach by prioritizing the most likely causes first (e.g., check for data pipeline issues or recent product changes) and quantifying their impact before exploring less probable ones. This shows efficiency and business acumen.

1. Clarify the metric and scope

Define what 'successful orders' means (e.g., completed, delivered, not canceled) and confirm the geographic market and time period. Ensure you understand any recent changes in tracking or definitions.

2. Segment the decline

Break down the decline by dimensions such as user cohort (new vs. existing), device, order type, restaurant partner, and time (daily/weekly). This helps localize the issue.

3. Generate hypotheses

List potential causes across internal factors (e.g., app bugs, pricing changes, delivery delays, marketing campaigns) and external factors (e.g., competitor promotions, weather, holidays, economic shifts).

4. Validate with data

For each hypothesis, identify data sources and analyses (e.g., funnel analysis, A/B tests, correlation with external events) to confirm or rule out causes. Prioritize based on likelihood and impact.

5. Synthesize and recommend

Summarize findings, quantify the impact of each cause, and propose next steps for deeper investigation or immediate action. Highlight any data limitations.

Key Points to Mention

  • Data quality checks: ensure the decline is real and not due to tracking errors or pipeline issues.
  • Segmentation: analyze by user type, device, geography (sub-regions), and time to isolate the problem.
  • Internal factors: recent product changes, pricing, promotions, delivery logistics, or app performance.
  • External factors: competitor actions, weather, holidays, economic conditions, or local events.
  • Funnel analysis: examine conversion rates at each stage (e.g., app open, search, checkout, delivery) to pinpoint drop-off.
  • Statistical significance: use hypothesis testing to confirm if changes are meaningful and not random noise.

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

Q2

Which metrics and data slices would you look at first when investigating this kind of drop?

Product Analytics & MetricsRoot Cause Analysis
Author's notes

Felt more comfortable here.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the metric definition and the scope of the drop (e.g., which metric, time period, and segment). Then systematically slice the data across dimensions like time, geography, user segments, and platform to isolate the source, and finally validate with statistical tests and cross-reference with external factors.

Pro tip: Always start with a data quality check—many apparent drops are due to instrumentation issues, logging errors, or pipeline failures. Mentioning this upfront shows you're pragmatic and have real-world experience.

1. Clarify the metric and drop

Confirm the exact metric definition, the magnitude and timing of the drop, and whether it's a sudden or gradual change. This ensures you're solving the right problem.

2. Check data quality and instrumentation

Verify that the drop is real by checking for logging errors, pipeline failures, or changes in data collection. Rule out false positives before diving deeper.

3. Slice by time and dimensions

Break down the metric by time (hourly, daily, weekly) and key dimensions such as geography, platform (iOS/Android/web), user cohorts, and acquisition channels to localize the drop.

4. Analyze user behavior and funnel

Examine upstream and downstream metrics in the user journey (e.g., sessions, conversion rates, order completion) to identify where the drop originates and its impact.

5. Correlate with external factors and validate

Check for concurrent events like app releases, marketing campaigns, competitor actions, or seasonality. Use statistical tests to confirm significance and avoid false conclusions.

Key Points to Mention

  • Metric definition and scope: ensure alignment on what exactly dropped (e.g., orders per user, conversion rate).
  • Data quality checks: rule out instrumentation, logging, or ETL issues before assuming a real drop.
  • Segmentation: slice by time, geography, platform, user demographics, and acquisition channel to isolate the affected segment.
  • Funnel analysis: trace the user journey to pinpoint the step where the drop occurs (e.g., app open, search, checkout).
  • External factors: consider app updates, marketing campaigns, holidays, competitor launches, or macroeconomic trends.
  • Statistical validation: use hypothesis testing or anomaly detection to confirm the drop is significant and not due to random variation.

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

Q3

How would you tell apart a demand-side problem, a supply-side problem, an operational issue, and a data instrumentation bug?

Root Cause AnalysisAdaptability & AmbiguityProduct Analytics & Metrics
Author's notes

This was the hardest part for me.

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AI HintsAI Generated

Suggested Approach

Start by defining each problem type in terms of its expected impact on key metrics and user behavior. Then propose a systematic diagnostic process that isolates the root cause by segmenting data across time, geography, user cohorts, and the supply-demand funnel. Emphasize the importance of validating data quality first before drawing conclusions.

Pro tip: Always check data instrumentation first—many apparent demand or supply issues are actually logging bugs. Use a 'trust but verify' mindset: cross-reference multiple data sources and run a quick sanity check on raw event counts.

1. Validate Data Integrity

Check for instrumentation bugs by verifying event logging, data pipelines, and metric definitions. Compare against source-of-truth systems and look for sudden drops or spikes in raw event counts.

2. Analyze Demand-Side Signals

Examine user-facing metrics like app sessions, search queries, order attempts, and conversion rates. If these drop while supply remains stable, it's likely a demand-side issue.

3. Analyze Supply-Side Signals

Look at dasher availability, acceptance rates, and delivery times. If demand is stable but supply metrics degrade, it's a supply-side problem.

4. Inspect Operational Metrics

Check for issues in order fulfillment, such as increased cancellations, delayed deliveries, or support tickets. Operational issues often manifest as bottlenecks in specific regions or times.

5. Synthesize and Isolate

Combine insights from steps 1-4 to pinpoint the root cause. Use segmentation (e.g., by market, time, user type) to confirm the problem type and rule out alternatives.

Key Points to Mention

  • Metric decomposition: break down high-level metrics (e.g., orders) into demand (sessions, conversion) and supply (dasher availability) components.
  • Data validation techniques: anomaly detection, pipeline monitoring, and A/B testing to rule out instrumentation bugs.
  • Segmentation analysis: compare across geographies, time periods, and user cohorts to localize the issue.
  • Funnel analysis: map the user journey from app open to delivery to identify where drop-offs occur.
  • External factors: consider seasonality, weather, holidays, or competitor actions that could affect demand or supply.
  • Cross-functional collaboration: work with engineering, operations, and product teams to validate hypotheses.

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

Q4

Walk me through one or two experiments you would run to validate a root cause and try to improve the metric. Include your primary metric, guardrails, and how you'd handle ambiguous results.

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

Proposed a pricing fee experiment and a merchant availability intervention.

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AI HintsAI Generated

Suggested Approach

Start by framing the problem with a clear hypothesis about the root cause and the metric you aim to improve. Then describe two experiments: one to validate the root cause (e.g., via a diagnostic A/B test or holdback) and one to test an improvement, specifying primary metric, guardrails, and how you'd interpret ambiguous results. Emphasize statistical rigor, practical significance, and decision-making under uncertainty.

Pro tip: Show you think beyond statistical significance: discuss effect size, confidence intervals, and business impact. Also, mention how you'd pre-register the analysis plan to avoid p-hacking and ensure trustworthy results.

1. Define the problem and hypothesis

Clearly state the metric to improve, the suspected root cause, and a testable hypothesis. Explain why this root cause is plausible based on data or domain knowledge.

2. Design experiment 1: Validate root cause

Propose an experiment that isolates the root cause, such as an A/B test where you manipulate the suspected factor. Specify primary metric, guardrails, sample size, and duration.

3. Design experiment 2: Test improvement

Outline a second experiment that implements a potential fix or improvement based on the validated root cause. Define success metrics, guardrails, and how you'll measure impact.

4. Analyze results and handle ambiguity

Describe how you'd analyze results, including checking for statistical significance, practical significance, and guardrail metrics. Explain how you'd handle ambiguous outcomes (e.g., inconclusive, mixed, or surprising results) with follow-up tests or deeper dives.

5. Make a decision and iterate

Summarize how you'd use the results to make a recommendation (ship, iterate, or abandon) and what next steps you'd take, emphasizing continuous learning.

Key Points to Mention

  • Primary metric selection (e.g., conversion rate, order completion time) and why it matters for DoorDash
  • Guardrail metrics (e.g., customer satisfaction, delivery time, cancellation rate) to ensure no negative side effects
  • Statistical power, sample size calculation, and minimum detectable effect
  • Handling ambiguous results: segment analysis, novelty effects, Simpson's paradox, and sequential testing
  • Practical significance vs. statistical significance and business impact
  • Pre-registration of analysis plan and avoiding p-hacking

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