Onsite: Project Deep Dive

Standalone deep-dive round (especially for MLE, Staff, and EM). DoorDash publishes a prep outline ahead of time: problem statement, your role, methods used, difficulties, success metrics. The interviewer drills on trade-offs, metric selection (offline / online / business), and post-launch learnings. Requirements Pick one project from your background. The recruiter typically sends a prep template before the round listing the expected dimensions: Problem statement — what you were solving, why it mattered. Your role — IC, lead, contributor; scope and ownership. Methods / approach — what you tried, what you picked, why. Difficulties — what was hard, how you handled ambiguity. Success metrics — offline (model metrics), online (A/B), business (revenue, retention). The round is 60 minutes; the interviewer typically gives 2–3 minutes of intro and then drills for 50+ minutes on tradeoffs. Notes DoorDash's prep template is detailed and unusual — use it. Multiple candidates report that following the template literally (problem → role → methods → difficulties → metrics, in that order) made the round flow smoothly. The interviewer especially probes: Trade-offs: why this design and not that one; what you'd change today. Metrics: offline metric definition (precision/recall/AUC/RMSE), how it relates to the online metric, how the online metric relates to business outcomes (orders, GMV, conversion). Post-launch behavior: what surprised you after launch, what you measured, what you iterated. For Staff / EM levels, expect XFN-impact drilling: who you worked with, how decisions were made, how you handled disagreement. Common failure mode: walking through the project as a narrative instead of answering each follow-up directly. Be concise; let the interviewer drive. Slide deck is optional but recommended for Staff and EM rounds; a 1-page architecture diagram materially helps. Don't pick the most recent project if it's still in flight — pick one with shipped metrics and a clear retrospective. The slide advice extends below Staff: in screening-slot deep dives the interviewer often follows the candidate's deck as the round's structure, interrupting for details. Expect one make-or-break ownership question — in a system this large, what exactly did you own — and answer with your specific scope rather than the team's. Embedded system-design format The project walkthrough can occupy the first approximately 25 minutes of a 75-minute system-design round instead of appearing as a standalone hour. Prepare a compact architecture-first version of the deck that can survive interruptions and still leave enough time for the assigned design prompt. MLE screening versions likewise follow recruiter-provided preparation material and use the candidate's slide deck as the conversation backbone. Preparation Use the DoorDash prep template literally. Fill it in before the round; rehearse to a friend in under 10 minutes. For each section, prepare 2–3 follow-up branches the interviewer might dive into (deeper into architecture, deeper into metrics, deeper into team dynamics). For Staff / EM: prepare a 1-slide architecture diagram and a 1-slide metrics dashboard. Prepare a clear "what I'd do differently" answer — interviewers almost always ask, and a generic "more testing" answer underperforms.