Describe experience working on a complex project
Asked at:
Udemy
Upstart
Netflix
Monzo
Try This Question Yourself
Practice with feedback and follow-up questions
What is this question about
Interviewers use this question to learn how you operate when the work is genuinely hard: unclear requirements, many moving parts, changing constraints, and non-trivial tradeoffs. They are usually assessing whether the complexity was real, whether your role matched your level, and whether you can explain not just what happened but how you brought order to it.
“Tell me about a technically or operationally complicated project you've worked on.”
“Walk me through a project that had a lot of moving parts. What made it hard?”
“What's an example of a project where the path forward wasn't obvious at the start?”
“Can you describe a challenging project you were deeply involved in and how you handled it?”
Key Insights
- You should define why the project was complex instead of assuming the interviewer will infer it. Complexity can come from ambiguity, scale, dependencies, risk, changing requirements, or operational constraints.
- Don't just narrate the project timeline. The strongest answers show your specific contribution: what you noticed, what decisions you drove, how you handled uncertainty, and what changed because of your work.
- For senior and above, complexity without leverage is incomplete. Show how you made the problem tractable for others through planning, decision-making, communication, or team-level structure.
What interviewers probe atlevel
Top Priority
You do not need to own the whole project, but you should clearly own a non-trivial slice and show how you moved it forward rather than waiting passively for direction.
Good examples
🟢I owned the integration for one part of the feature, and when I found data mismatches I traced them through the flow, proposed a fix, and coordinated testing with the teammate on the upstream service.
🟢I was responsible for the validation layer, and beyond implementing it I documented edge cases, added checks that caught bad inputs early, and made sure support knew what errors users would see.
Bad examples
🔴My lead broke the project into tasks for me and I kept checking back whenever I got stuck, which helped me finish my assigned pieces correctly.
🔴I mostly focused on writing the code I was told to write, and when issues came up I escalated them quickly so the team could decide what to do.
Weak answers show execution of assigned work only; strong answers show initiative, follow-through, and responsibility for outcomes within an appropriate slice.
At junior level, interviewers do not expect huge scope, but they do expect a real challenge with enough moving parts that you had to think, learn, and adapt rather than just follow instructions.
Good examples
🟢It was my first feature that touched three services, and the complexity was that a small change in one place affected data shape, error handling, and monitoring in another, so I had to understand the end-to-end flow before coding.
🟢The challenge wasn't scale but uncertainty: the expected behavior was only partly documented, so I had to compare current system behavior, ask clarifying questions, and validate edge cases before implementing my part.
Bad examples
🔴It was a complex project because the codebase was new to me, so I mostly spent time figuring out where things were and then implemented the tickets my mentor gave me.
🔴The project was hard because the deadline was short, but the work itself was pretty standard CRUD work and I mainly just had a lot to do.
Weak answers confuse personal unfamiliarity or busyness with project complexity; strong answers explain objective complexity in the work itself and why it required deeper reasoning.
Valuable
You don't need executive-level polish, but you should show proactive communication: surfacing unknowns, asking clear questions, and keeping relevant people informed.
Good examples
🟢I sent concise updates when I found risks, including what I had checked already and the decision I needed, which made it easier for my mentor and teammate to help quickly.
🟢Because several people touched the feature, I documented the expected behavior and edge cases so testing and implementation stayed aligned.
Bad examples
🔴I mostly communicated through code reviews and only brought things up when someone asked for an update.
🔴When I was unsure about some requirements, I waited until the next team meeting to ask so I wouldn't interrupt anyone.
Weak answers make communication passive; strong answers show communication as a tool for reducing confusion and rework.
A good junior answer shows resilience, but not stubbornness—you should demonstrate that when something failed, you learned, adapted, and kept moving.
Good examples
🟢After my initial implementation exposed performance issues, I compared two simpler alternatives, asked for a quick review of my reasoning, and switched to the safer option.
🟢When I got blocked by inconsistent test data, I stopped guessing, built a minimal reproduction, and used that to confirm the real issue before continuing.
Bad examples
🔴When my first approach didn't work, I spent a long time trying small variations until eventually the tests passed.
🔴The integration kept failing, so I kept debugging on my own for most of the week because I wanted to solve it independently.
Weak answers show persistence without learning; strong answers show persistence guided by reflection and course correction.
Example answers atlevel
Great answers
One complex project I worked on was adding a new account recovery flow to an internal product during my first year. It was complex for me because the change touched the frontend, an API, and an older authentication service, and the expected behavior wasn't fully documented. I owned the API changes and the validation logic, so I started by mapping the current flow, listing the unknowns, and confirming edge cases with my mentor and QA before I wrote much code. During testing I found that one service returned inconsistent error formats, which would have broken the user flow, so I traced the issue, proposed a small normalization layer, and coordinated with the teammate who owned that service. We released behind a flag, watched the first few days closely, and the rollout was smooth. What I learned was that on projects that seem complicated at first, making the unknowns explicit early saves a lot of rework.
At my last internship I helped add an offline mode to a small cross-platform mobile app used by field technicians, which felt complex because it touched storage, sync logic, and the UI for conflict handling. I was responsible for the local data layer and tests, so I worked closely with a senior engineer and the product manager to decide the simplest conflict-resolution rules we could accept. While writing tests I uncovered a case where a crash during sync could lose recent updates, so I implemented atomic writes and improved the retry logic with guidance from my mentor. We rolled out the feature to a small pilot group, collected quick feedback, and fixed a couple UX issues (like unclear sync status) before wider release. The biggest lesson I took away was that on small teams, shipping a minimal, well-tested solution and showing it to real users early prevents most surprises.
Poor answers
A complex project I worked on was building a dashboard for our team. It was complex because the codebase was new to me and there were a lot of files to understand. My lead gave me a set of tasks and I worked through them one by one, asking questions when I got stuck. It took a while, but I finished everything that was assigned to me and the dashboard launched on time. Overall I think it went well because I was able to get through a large amount of work.
Question Timeline
See when this question was last asked and where, including any notes left by other candidates.
Early July, 2026
Arize AI
Senior
Early July, 2026
Sprinter Health
Senior
Early June, 2026
Netflix
Senior
Hello Interview Premium
Your account is free and you can post anonymously if you choose.