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DoorDash·Data Scientist·Technical Phone Screen·Senior

SeniorPrefer not to say
Jul 2026

Summary

DoorDash data science case focused entirely on a marketplace expansion problem: should bike dashers be allowed in a city currently dominated by cars and scooters. It was a deep, multi-part question that touched on everything from experiment design to network effects, and I left feeling like I'd only scratched the surface on a few of the sub-parts.

Questions Asked (5)

Q1

What historical marketplace data would you look at to determine whether a city or specific zones within it are good candidates for bike dashers?

Product Analytics & MetricsProduct Sense & Ideation
Author's notes

This part felt manageable.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the goal: to identify cities or zones where bike dashers can operate efficiently and meet demand. Then outline a data-driven framework that evaluates demand, supply, and operational feasibility using historical marketplace data. Structure your answer around key metrics and how they inform the decision.

Pro tip: Emphasize the importance of unit economics and the balance between demand density and supply availability. Mention that you would validate hypotheses with A/B tests or pilot programs before full rollout.

1. Define success criteria

Clarify what makes a city or zone 'good' for bike dashers, such as high delivery volume, short distances, and low cost per delivery. Align these criteria with business goals like profitability and customer satisfaction.

2. Identify relevant data sources

List historical marketplace data such as order volume, delivery times, dasher supply, and geographic data. Consider external data like weather and bike infrastructure if available.

3. Analyze demand patterns

Examine order density, peak times, and seasonality to assess if demand is sufficient and consistent for bike couriers. Look at order sizes and restaurant types to ensure they are bike-friendly.

4. Evaluate supply and competition

Assess current dasher supply, including bike dashers if any, and competition from other delivery services. Determine if there is a gap that bike dashers can fill.

5. Assess operational feasibility

Analyze average delivery distances, traffic conditions, and infrastructure (e.g., bike lanes). Calculate potential delivery times and costs for bike vs. car to see if bikes are competitive.

Key Points to Mention

  • Order density and delivery distance distribution
  • Dasher supply and utilization rates
  • Cost per delivery and profitability metrics
  • Seasonality and weather impact on bike deliveries
  • Local infrastructure and regulations for bikes
  • Competitive landscape and market share potential

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

Q2

What primary, secondary, and guardrail metrics would you track across consumer, merchant, dasher, and unit economics dimensions when evaluating bike dashers?

Product Analytics & MetricsA/B Testing & Experimentation
Author's notes

I spent too long on consumer metrics and had to rush through dasher and merchant sides.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the goal of evaluating bike dashers—likely to assess their impact on delivery efficiency, cost, and experience across all stakeholders. Then, for each dimension (consumer, merchant, dasher, unit economics), define primary metrics that directly measure success, secondary metrics that provide additional context, and guardrail metrics to ensure no harm. Finally, discuss how these metrics interact and potential trade-offs.

Pro tip: Emphasize that guardrail metrics are crucial to catch unintended consequences, such as longer delivery times for consumers or increased costs, and mention that bike dashers might be more effective in dense urban areas, so segment your analysis by market density.

1. Clarify the objective and scope

Confirm that the evaluation is about the impact of bike dashers on the platform, and identify key hypotheses (e.g., bike dashers improve speed in urban areas but may have limited range).

2. Define metrics for each dimension

For consumer, merchant, dasher, and unit economics, list primary, secondary, and guardrail metrics. Ensure primary metrics align with the dimension's core goal.

3. Explain metric selection rationale

Briefly justify why each metric is chosen, especially guardrails that prevent negative side effects (e.g., consumer wait time as a guardrail for delivery speed).

4. Discuss interactions and trade-offs

Highlight how metrics across dimensions interact (e.g., faster delivery may increase consumer satisfaction but raise dasher costs) and how to balance them.

5. Suggest analysis approach

Mention segmenting by market density, comparing bike vs. car dashers, and using A/B tests or causal inference to measure impact.

Key Points to Mention

  • Consumer: Primary - delivery time; Secondary - order accuracy, app rating; Guardrail - cancellation rate, customer support contacts.
  • Merchant: Primary - order volume; Secondary - preparation time, merchant satisfaction; Guardrail - order accuracy, refund rate.
  • Dasher: Primary - deliveries per hour; Secondary - earnings per hour, active time; Guardrail - safety incidents, dasher satisfaction.
  • Unit economics: Primary - delivery cost per order; Secondary - contribution margin; Guardrail - overall profitability, cost per delivery.
  • Segment by market density (urban vs. suburban) and compare bike vs. car dashers.
  • Use A/B testing or quasi-experimental methods to isolate the impact of bike dashers.

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

Q3

How would you design an A/B test or marketplace experiment to measure the causal impact of enabling bike dashers in a city?

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

Went with a geo-based holdout design, splitting zones rather than individual orders.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the goal: measure the causal impact of enabling bike dashers on key marketplace metrics like delivery time, order volume, and dasher utilization. Then propose a randomized controlled experiment at the city or sub-region level, considering interference and spillover effects, and outline how to analyze the results with appropriate statistical methods.

Pro tip: In marketplace experiments, interference between treatment and control units is a major concern; consider using a switchback or cluster randomization design to mitigate it. Also, pre-register your metrics and guardrails to avoid p-hacking and ensure stakeholder alignment.

1. Define Hypothesis and Metrics

Clearly state the hypothesis: enabling bike dashers will improve delivery efficiency and customer experience. Select primary metrics (e.g., delivery time, order completion rate) and guardrail metrics (e.g., dasher earnings, customer ratings).

2. Choose Randomization Unit and Design

Decide whether to randomize at the city, zone, or order level. For marketplace experiments, consider cluster randomization or switchback designs to handle interference and spillover effects.

3. Determine Sample Size and Power

Calculate required sample size based on expected effect size, variance, and desired power (e.g., 80%) and significance level (e.g., 5%). Account for intra-cluster correlation if using cluster randomization.

4. Run Experiment and Monitor

Launch the experiment, monitor for data quality issues, and ensure no SRM (sample ratio mismatch). Track guardrail metrics to detect any negative impact early.

5. Analyze Results and Make Decision

Use appropriate statistical tests (e.g., t-test, regression with fixed effects) to estimate causal impact. Consider heterogeneous treatment effects and conduct sensitivity analysis. Provide a clear recommendation based on statistical and practical significance.

Key Points to Mention

  • Randomization unit: city, zone, or order level; trade-offs between bias and variance
  • Interference and spillover effects in marketplaces; mitigation via cluster randomization or switchback
  • Primary and guardrail metrics: delivery time, order volume, dasher utilization, customer satisfaction
  • Sample size calculation and power analysis, accounting for clustering
  • Analysis methods: intent-to-treat, difference-in-differences, or causal inference techniques
  • Practical significance vs. statistical significance; business impact and rollout decision

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

Q4

Bike dashers affect dispatch and matching for all orders in a zone, not just their own. How do you account for these spillover effects in your experiment design and analysis?

A/B Testing & ExperimentationTechnical Trade-offs
Author's notes

This is where things got hard.

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AI HintsAI Generated

Suggested Approach

Acknowledge that bike dasher interventions create interference through shared dispatch and matching, violating the stable unit treatment value assumption (SUTVA). Propose designs that randomize at the zone or market level, or use switchback or cluster randomization, and analyze with methods that account for spillovers such as network effects or spatial correlation. Emphasize measuring both direct and indirect effects to capture the full impact on all orders in the zone.

Pro tip: Highlight the trade-off between bias and variance: cluster randomization reduces spillover bias but increases variance, so consider using a combination of within-cluster and between-cluster comparisons or synthetic control methods to improve precision.

1. Identify and quantify spillover mechanisms

Map how bike dashers affect dispatch and matching for other orders, such as by changing the pool of available dashers, altering delivery times, or shifting order assignments. Quantify the potential magnitude of these effects to inform design choices.

2. Choose an appropriate randomization unit

Select a unit that minimizes interference, such as zone, city, or time-based switchback, depending on the scale of spillovers. If spillovers are local, consider cluster randomization at the zone level; if temporal, use switchback designs.

3. Design the experiment to measure direct and indirect effects

Include conditions that allow estimation of both the direct effect on treated dashers and the spillover effect on untreated dashers and orders. For example, use a saturation design or two-stage randomization to vary the proportion of treated dashers in a zone.

4. Analyze with methods that account for interference

Apply statistical techniques such as cluster-robust standard errors, spatial regression, or causal inference methods for interference (e.g., exposure mapping, network effects). Compare results with and without adjustments to assess sensitivity.

5. Validate and interpret results in context

Check for remaining confounding and ensure that the estimated effects are generalizable. Interpret the business impact considering both direct and spillover effects, and communicate the trade-offs and limitations.

Key Points to Mention

  • SUTVA violation and interference in two-sided marketplaces
  • Cluster randomization (e.g., zone-level) vs. switchback designs
  • Saturation designs to vary treatment intensity within clusters
  • Measuring direct and indirect (spillover) effects
  • Using exposure mapping or network-based causal inference methods
  • Trade-off between bias reduction and variance inflation in clustered designs

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

Q5

What experimental outcomes would lead you to fully launch, partially roll out, or pull back the bike dasher program?

Product StrategyAdaptability & Ambiguity
Author's notes

Decent answer.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the program's success metrics and the experimental design, then define decision thresholds based on statistical significance and practical impact. Structure your answer around a decision framework that maps outcomes to launch, partial rollout, or pullback, emphasizing data-driven trade-offs.

Pro tip: Show that you consider both statistical and business significance, and mention the importance of segment-level analysis to avoid Simpson's paradox. Also, highlight the need for a holdout group to measure long-term effects.

1. Define success metrics and guardrails

Identify primary metrics (e.g., order completion rate, delivery time) and guardrail metrics (e.g., customer satisfaction, Dasher safety) that determine program success.

2. Set decision thresholds

Establish quantitative thresholds for launch, partial rollout, and pullback based on minimum detectable effect, business goals, and risk tolerance.

3. Analyze experiment results

Evaluate statistical significance, confidence intervals, and practical impact on metrics, checking for heterogeneous treatment effects across segments.

4. Map outcomes to decisions

If primary metrics improve significantly with no guardrail violations, fully launch; if mixed results or only some segments benefit, partially roll out; if negative or no effect, pull back.

5. Consider next steps

For partial rollout, propose further experiments or targeted improvements; for pullback, suggest learnings and alternative approaches.

Key Points to Mention

  • Statistical significance and confidence intervals
  • Practical significance and effect size
  • Guardrail metrics to detect unintended consequences
  • Segment analysis for heterogeneous effects
  • Long-term impact and novelty effects
  • Cost-benefit analysis and scalability

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