Marketplace / delivery
DoorDash interview themes
What people report studying for — not a take-home dump. Last editorial update 2026-09-12.
Rounds you should expect
SQL
One row per delivery vs per item. Which metrics fan out if you pick wrong.
Streaming
A courier ping is 8 minutes late. Event time vs the 09:00 dashboard.
Features
Online/offline parity for an ETA model. Warehouse is the wrong 20 ms path.
From the question bank
medium · SQL · SQL
Running total of daily revenue. Why is SUM(SUM(amount)) OVER (...) valid?
Practice →medium · SQL · SQL
A date spine is missing Sundays. What breaks in a 7-day rolling metric?
Practice →hard · Streaming · Kafka
What is a poison pill, and how do you not stall the whole partition?
Practice →hard · AI / ML · AI / RAG / MLOps
Feature store vs “a gold table named features.” What is the extra work?
Practice →medium · AI / ML · AI / RAG / MLOps
Online vs offline features for the same model.
Practice →hard · AI / ML · AI / RAG / MLOps
Offline feature table has 40 columns; online store has 12. The model’s AUC collapsed after deploy. First check?
Practice →medium · System design · System design
Design an orders platform for 40 analysts at 9:00 and a 15-minute CDC lag. Sketch the layers.
Practice →hard · System design · System design
When is a warehouse the wrong serving plane?
Practice →easy · System design · System design
Streaming dashboard vs a 1-hour mart. How do you choose?
Practice →medium · System design · System design
Online store for features must answer in 20 ms. Warehouse p95 is 800 ms. What is the serving path?
Practice →medium · Orchestration · Dagster
A late partition arrived. What must not happen?
Practice →easy · Data quality · Data quality
Where should the contract live — producer or warehouse?
Practice →