Here are 6 answers that work well for FAANG and other engineer interviews. Pick one or two that feel closest to something you’ve actually lived, then scroll down to find the full example below.
The over-engineering failure
You built a system to handle 50M requests per second, the traffic never came.The estimation failure
You said yes to a timeline you couldn’t hit because you didn’t want to push back.The shortcut failure
You took a shortcut under pressure, and you/someone else paid for it.The assumption failure
You assumed alignment because nobody told you otherwise.The communication failure
You were right about the technical direction, but wrong about how you pushed for it.The heads-down failure
You went too deep on a problem and came up with the wrong thing.
By the way, if you’re a manager, your stories should look very different from this. This article is for you:
How to pick a story?
If you are not sure what kind of failure to pick? Know this - a good answer to this question is about your judgment, not your bad luck.
When asked “tell me about a mistake you made,” or “a time you failed,“ many engineers default to telling a post-mortem - the system broke, here’s the root cause, here’s the fix.
The problem here is that the interviewer needs to write something in the debrief about what you specifically learned and changed, and if you spend 80% of your time talking about a broken system, they don’t get that - and you don’t get the job or get down-leveled.
If your best story is “we missed a deadline” or “the system went down,” reframe it around the call you got wrong. “There was an outage” is an incident report. “I pushed to prod without a canary because I was confident it was low-risk” is a judgment failure.
Also, see my note in the end about “picking your level.”
IMPORTANT: Finally, avoid anything where you’re blaming someone else (even partially), anything involving HR or legal situations, and the classic “I’m too much of a perfectionist” - interviewers have heard that one approximately four hundred thousand times.
Sample Failure Answers for Engineers
Here are 6 carefully crafted answers that are about “judgement” vs “post-mortem”, and signal humility and agency (what interviewers are looking for) using my 5-point failure story arc.
1. The over-engineering story - “the perfect design no one asked for”
The failure: Your team needed a data pipeline for a single-market feature. You’d heard in a planning meeting that the product might expand to three more markets, so you designed for all four - configurable ingestion, multi-tenant storage, cross-region fallback, what not - ended up taking 10 weeks (pre-AI era) instead of 4. And… the expansion… got deprioritized in Q3.
The diagnosis: You’d made an architecture decision based on a hallway conversation, not a product commitment.
What you did: You brought it up with your manager before she had to ask. Walked her through where the extra weeks went, and why the assumptions behind them didn't hold up.
The lesson: Designing for a roadmap that doesn’t exist is speculation, not foresight.
What changed: You now ask one question before adding flexibility: “Is there a committed use case for this in the next two quarters?” If no, you design a clean extension point and move on. "Last quarter, my team needed a notification service. Someone suggested building it multi-channel from day one. I asked if we are going to add new channels in the next 6 months, and the answer was no. So we built for email only with a clean interface to swap later, and it took 3 weeks instead of 7."
If this reminds you of a time you built something technically elegant that nobody needed, that’s your story.
Get the remaining five stories for FREE by signing up - the diagnosis-and-fix breakdown for each, and how to pick the right one for your level.
