← DoorDash Interview Insights

DoorDash·Data Scientist·Technical Phone Screen·Senior

SeniorPrefer not to say
May 2026Remote

Summary

DoorDash DS interview, one big meaty experiment design question that covered basically every angle you can think of. Felt like a take-home disguised as a live question. Walked away not totally sure if I nailed it or just sounded like I knew what I was talking about.

Questions Asked (1)

Q1

DoorDash is testing a new batching policy where a dasher can pick up two nearby orders in one trip during peak hours. Design a full experiment to measure causal impact on order conversion rate, ETA accuracy, dasher hourly earnings, and restaurant prep-time congestion. Cover your randomization unit, stratification, sample size, novelty effects, heterogeneous treatment effects, and your decision rule when guardrails and primary metrics point in opposite directions.

A/B Testing & ExperimentationProduct Analytics & MetricsData Modeling
Author's notes

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AI HintsAI Generated

Suggested Approach

Start by clarifying the business objectives and defining primary vs. guardrail metrics, then design a randomized experiment with appropriate unit (e.g., dasher or order) and stratification to ensure balance. Address practical challenges like novelty effects, heterogeneous treatment effects, and conflicting metrics by pre-registering a decision framework that weighs trade-offs.

Pro tip: Propose a switchback or cluster randomization if interference between orders is a concern, and emphasize the importance of pre-registering the analysis plan to avoid p-hacking when metrics conflict.

1. Define Metrics and Hypotheses

Clearly specify primary metrics (order conversion rate, ETA accuracy, dasher hourly earnings, restaurant prep-time congestion) and guardrail metrics (e.g., customer satisfaction, dasher safety). State directional hypotheses for each.

2. Choose Randomization Unit and Stratification

Select randomization unit (e.g., dasher, order, or time-based switchback) based on interference risk. Stratify by key covariates like market, time of day, and restaurant density to improve power and balance.

3. Determine Sample Size and Power

Conduct power analysis for each primary metric, accounting for multiple comparisons. Use historical data to estimate variance and minimum detectable effect (MDE), then calculate required sample size per arm.

4. Address Novelty and Heterogeneity

Plan for novelty effects by running the experiment long enough and analyzing early vs. late periods. Pre-specify subgroups (e.g., dasher tenure, restaurant type) to explore heterogeneous treatment effects.

5. Pre-Register Decision Rules

Define a decision framework that prioritizes primary metrics while respecting guardrails. Specify thresholds for success, failure, and conditions for further iteration when metrics conflict (e.g., primary improves but guardrail degrades).

Key Points to Mention

  • Randomization unit: dasher-level vs. order-level vs. switchback design to handle interference
  • Stratification by market, time of day, and restaurant density to reduce variance
  • Power analysis and sample size calculation for multiple metrics with corrections (e.g., Bonferroni)
  • Novelty effect mitigation: run experiment for multiple weeks and analyze trends
  • Heterogeneous treatment effects: pre-specified subgroups like dasher experience and restaurant cuisine
  • Decision rule: pre-register trade-off criteria, e.g., primary must improve by X% without guardrail degrading more than Y%

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