Chapter 25 · Free companion · A practice room

The Ambiguous Case Study

The round no other engineering interview prepares you for — and the one most candidates fail. It is also the most learnable, because almost nobody practises it and the thing being measured is a procedure rather than a talent.

~40%pass rate
~30%of loop weight
45–60minutes
0correct answers

What is being measured

An interviewer plays a customer. They describe a problem the way a real customer does — vaguely, in their own vocabulary, with the solution already assumed. There is no right answer. There is a right behaviour, and it is being scored.

You are not being graded on the plan you produce. You are being graded on how you got there.

Pick a case

Work it aloud, against a timer, ideally with someone playing the customer. Written answers do not build the skill — the round is verbal and the pressure is the point.

Drill one — ten minutes, questions only

Before any solution, any architecture, any technology. Write only the questions you would ask. This is the drill that most changes interview outcomes, because solving too early is the most common failure and you cannot feel yourself doing it.

10:00
questions: 0 · open-ended: 0
Only after the timer — what is actually going on in this case

The procedure — six moves

In this order. Under pressure people skip to move four; the skip is the failure.

    Score yourself

    Reconstructed from how these rounds are actually assessed. Score honestly after each practice run. Passing is roughly a 3 across the board with two 4s — but offers cluster where framing and evidence-seeking are 4–5, because those two predict field behaviour better than the rest combined.

    Dimension1 — weak · 3 — solid · 5 — strong

    The five failure modes