A practice prompt we wrote. No company or candidate report names it, so it carries no company tag.

How to answer

The second half carries the weight: without a named flip condition, a decision sounds like a preference.

  1. The need and the clock. What the customer needed, by when, and who would run it after you left. For an that can decide it, because the customer’s team inherits your choice.
  2. The options you compared. Buy, build, extend what they already run, or buy now and build later.
  3. Total cost, not license cost. Build: engineering time, maintenance, on-call, and whoever understands it after you leave. Buy: license, integration, the gaps you’d work around, lock-in. Put rough figures on each.
  4. Time to value. When each would reach users. At a large customer, procurement and security review count in buy’s time and can outlast the build.
  5. The decision, who signed it, and the flip condition. What you chose, the one-page comparison you gave whoever signed, and the fact that would have reversed it: “If the vendor couldn’t keep each region’s data in that region by the pilot, I’d have built.”
  6. What happened. Cost and time against your estimate, and whether the condition came close.

Say the flip condition as a threshold you checked, not a feeling: “I asked the vendor for a written answer on before we signed.”

Colin Jarvis of OpenAI said on a South Park Commons panel in May 2026 that one failure pattern is people who come to love the form of what they built more than its function. Source 1The Future of Forward Deployed Engineering | OpenAI, Ramp, Nominal, DatalandPublisherSouth Park Commons (YouTube)Source typerecorded talk or interview If your story ends in a build, show you weren’t one of them: say what, after launch, would have made you switch to the vendor.

The traps: license price against your own time valued at zero, a decision someone else made told as yours, and a flip condition that could never have happened.

GlossaryForward deployed engineerA software engineer who builds and ships production systems inside a customer’s problem and environment, accountable to that customer’s outcome.More on Forward deployed engineerGlossaryData residencyA requirement that data, including logs and backups, be stored and processed in a specific region.More on Data residency

Follow-ups

What the interviewer may ask next, once your first answer is on the table.

  • Who ran it after you left, and what did it cost them to keep running?
  • Did the condition that would have flipped your decision ever come close to happening?
  • Knowing what you know now, would you make the same call, and what would it cost the customer to switch today?

Where answers go wrong

  • Compares the license price with a build cost that counts only their own engineering time, leaving out maintenance, on-call and who owns it after handoff.
  • Can’t name what would have changed their mind, or names a condition that could never happen, so the decision sounds like a preference.

Answer this in two minutes

Write the answer you would say out loud. The clock starts with your first word.

Two minutes

Illustrative answer about a fictional project

I was deploying call summaries for a credit union’s member-services team: every call transcribed, then summarized by a language model into the member’s record. Their risk team had one condition: account numbers, card numbers and dates of birth had to be removed before any transcript reached the model.

Learn this in Module 3: Client simulation and customer judgment, part of the curriculum.