DoorDash Senior+ Software Engineer Interview Experience — Four-Round Virtual Onsite With an Incident Simulation

DoorDash·Software Engineer·Jul 2025
OnsiteSenior+Rejectedhard

Virtual Onsite, four rounds total. First round simulated handling an Incident. Second round System Design, third round Coding, fourth round HM (Hiring Manager).

Incident

Assume we own a payment integration service. Internally, various services call us to make payments, and downstream from us is a financial institute. The current incident shows our service is abnormal, with high CPU and memory usage. That's where it starts.

I say what I want to do next, and the interviewer gives me a mock result — basically what I'd see if I did that. If something isn't possible, they'd say we don't have that support.

Check infra status. Result: most auto-scaling nodes are down. Every new auto-scaling node that comes up dies right away.
Check traffic — incoming calls from upstream are 10x normal.
Check the nodes' errors going downstream — all client timeouts, no other specific info.
Check deployments — no new deployment in the past 24 hours (they said to assume this isn't caused by a recent bug).

The steps I gave were mitigate -> root cause -> follow-up action.

System Design

The question was to design an Instagram. My approach basically followed that YouTube video of a Meta guy designing Twitter.

Coding

OO design, coding a key-value store, but the key is a path linked by '/'. The root node is '/', with value '#'.
All values are strings. Support Create, SetValue, GetValue, Delete operations.
Create requires the parent node to exist, GetValue requires the node to exist, Delete requires the node to have no children.

HM

I think this round was the key reason I got dinged. The HM was on leave, so it got swapped to an older man with graying hair asking instead. The whole round was about my experience leading past projects and whether I'd helped teammates grow. But the whole Q&A felt like being interrogated.

The interviewer mainly challenged that I'd only helped college students grow in a community project. At the Google L5 level, I hadn't shown I could help teammates grow. And on my highest-scope project, I wasn't the one in a leadership position.

Published

Curated and edited by PracHub

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Interview at a glance

Company
DoorDash
Role
Software Engineer
Level
Senior+
Rounds
Onsite
Outcome
Rejected
Difficulty
hard
Interview date
Jul 2025
Questions from this interview
4 questions

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