Senior Project Deep Dive: Design Rationale, Your Most Complex Project, Questions for the HM

Two parts of an onsite loop for a senior software engineer on an AI infrastructure team probed the candidate's past work. In a resume deep dive, the interviewer picked projects from the resume and discussed their technical core in depth: why each was designed the way it was, and which alternatives were considered. The hiring manager round came last, after a full day of interviews; the hiring manager asked for the most complex project you have worked on, and then asked what questions you had for them. The hiring decision in this loop weighed two senior-level signals beyond technical ability: whether the scope of your past projects matches senior expectations, and whether you show the habit of asking probing questions. Answer each part as you would in the room. ### Clarifying Questions - Should the deep-dive project be the most recent one, or the one most relevant to infrastructure work? - For the most complex project, is the interviewer more interested in technical depth or in the breadth of teams and systems involved? - How much time is there for each answer, and would you like a short overview before going deep? ### Part 1 — Resume deep dive: design rationale and alternatives Choose a technically substantial project from your resume. Explain its architecture and its key design decisions, why each decision was made, and which alternatives you considered and rejected. Expect repeated "why?" questions on the same technical points. ```hint Prepare the options you rejected For each major decision, be ready to name the option you did not take and the constraint that ruled it out. ``` #### What This Part Should Cover - The key technical decisions and the constraints that drove them - Named alternatives, why they lost, and when they would have been the better choice - Technical detail that stays consistent under repeated probing ### Part 2 — Your most complex project The hiring manager asks: what is the most complex project you have worked on? Present it so the interviewer can judge its scope as well as its technical difficulty. ```hint Say what made it complex Decide in advance whether the complexity came from technical depth, from the number of teams and systems involved, or from ambiguity in the problem itself, and make that explicit early in the answer. ``` #### What This Part Should Cover - Why the project was complex, across technical, organizational and ambiguity dimensions - Your personal role in defining the problem, setting direction and driving it across teams - Measurable outcomes and what you would do differently ### Part 3 — Your questions for the hiring manager The hiring manager asks what questions you have for them. ```hint Ask, then ask again Plan questions about the team's real problems, and plan how you would follow up on each answer instead of moving straight to your next question. ``` #### What This Part Should Cover - Questions that probe the team's technical challenges, priorities and expectations for this role - Follow-up questions that build on the answers you get - Evidence that you would evaluate the problem space the way a senior engineer does ### What a Strong Answer Covers - A project whose scope visibly matches the senior level: several teams or systems, ambiguity you resolved, and decisions with lasting consequences - A clear boundary between your own contribution and the team's - Numbers and outcomes that make scope and impact concrete - Probing, well-sequenced questions, both while clarifying and at the end - Answers prepared well enough to stay crisp at the end of a long interview day ### Follow-up Questions - Which design decision on that project would you reverse today, and what would changing it cost now? - How did you get other teams to agree to the direction you proposed? - If the project had to be delivered with half the team, what would you cut, and why? - What did you personally do when the project hit its biggest setback?