How would you prevent wrong items in deliveries?
Company: DoorDash
Role: Machine Learning Engineer
Category: Behavioral & Leadership
Difficulty: medium
Interview Round: Onsite
## Behavioral / Product-Process Scenario
You work on a food delivery platform. Customers sometimes receive the **wrong items** (restaurant packed incorrectly, driver picked up wrong bag, labels missing, etc.).
### Prompt
Explain how you would **maximize the reduction of wrong-order incidents**. Cover:
- How you would diagnose root causes (restaurant vs driver vs app flow)
- What process and/or technical changes you would introduce
- How you would measure success and manage trade-offs (time at pickup, cost, merchant friction)
- How you would roll out changes safely
Quick Answer: This question evaluates systems thinking, root-cause analysis, metrics-driven decision-making, and cross-functional leadership in operational product-process contexts.
Solution
### 1) Structure the answer (shows leadership)
Use a clear frame:
1. **Define the problem + metric**
2. **Find root causes** (data + qualitative)
3. **Generate mitigations** (process + product + engineering)
4. **Prioritize** by impact/effort and stakeholder friction
5. **Pilot + measure + iterate**
---
### 2) Define metrics and scope
Primary metric (choose one and define precisely):
- **Wrong-order rate** = wrong-item reports / completed deliveries
- Or **cost rate** = refunds + credits due to wrong items / GMV
Guardrails:
- Pickup time / courier wait time
- Merchant acceptance / churn
- Customer satisfaction (CSAT), re-order rate
- Fraud rate (false claims)
Segment metrics by:
- Merchant, merchant size, cuisine
- Courier experience tier
- Order complexity (#items, modifiers)
- Packaging type (sealed vs unsealed)
---
### 3) Diagnose root causes
Combine:
- **Customer support tags** (wrong item, missing item, wrong order, tampered seal)
- Courier app events (arrived, picked up, photo, barcode scan)
- Merchant POS/integration signals (order acknowledged, printed, packed)
Create a simple attribution taxonomy:
- **Merchant packing error** (wrong/missing items)
- **Courier pickup mix-up** (picked wrong bag)
- **Handoff labeling issue** (no label, illegible label)
- **Customer misreport / fraud**
Then identify top contributors via Pareto: e.g., top 5% merchants cause 40% of incidents.
---
### 4) Intervention ideas (process + product)
#### 4.1 Low-cost process controls (fastest wins)
- **Standardized packing checklist** in merchant tablet/POS (especially for modifiers).
- **Prominent order label**: customer name + order ID + item count.
- **Sealed packaging requirement** and seal integrity guidance.
#### 4.2 Pickup verification (the “extra check” mechanism, but done thoughtfully)
Goal: verify without adding too much friction.
- **Scan-based verification**: barcode/QR on the bag label scanned by courier.
- App validates it matches the order ID.
- Works best when the platform prints labels or provides QR.
- If scanning isn’t feasible: **photo confirmation** at pickup (bag label visible) for high-risk merchants/orders.
- **Two-person confirmation** at merchant for high-incident locations (operational playbook, not everywhere).
Trade-off: Added pickup time. Mitigation: only enforce on **high-risk segments** (merchant/order score).
#### 4.3 Reduce merchant packing errors
- UI improvements in merchant app:
- Highlight modifiers ("no onions")
- Group items by station (hot/cold)
- "Mark item packed" flow for complex orders
- For integrated merchants: send structured item/modifier data; ensure printer formatting is clear.
#### 4.4 Courier-side improvements
- Stronger pickup UX: show **bag count** expected, store pickup notes.
- Training/nudges for new couriers; "repeat offender" coaching.
#### 4.5 Fraud/false-claim controls (careful)
- Require photo evidence for certain claim types.
- Use anomaly detection to flag repeated claim patterns, but avoid punishing legitimate users.
---
### 5) Prioritization and rollout
Prioritize by **Impact × Confidence / Effort**.
- Start with top incident merchants (targeted rollout).
- A/B test verification flows (scan vs photo vs none) with guardrails on pickup time.
- Roll out gradually (1 city → 10 cities) with monitoring.
---
### 6) Measurement plan
Success looks like:
- Wrong-order rate down (overall and in targeted segments)
- Refund cost down
- No significant regression in pickup time or courier churn
- Merchant satisfaction acceptable
Also monitor substitution effects:
- Wrong-item reports may drop but **missing-item** reports rise (packing checklist partially helps both).
---
### 7) Close with stakeholder alignment
Call out that this is cross-functional:
- Merchant ops (training, compliance)
- Courier ops (workflow)
- Product/eng (labeling, scanning, telemetry)
- Support (taxonomy + feedback loop)
A strong interview answer explicitly balances **customer trust**, **operational friction**, and **scalability** of the solution.