TL;DR: Intervene on process, not personalities: name what is happening without blame, force the argument onto written, testable criteria (cost, risk to SLOs, migration effort), park it with an owner and a deadline if it cannot resolve live. The failure modes are refereeing a winner or letting silence bury the disagreement.
How to approach it
Walk through the moment chronologically: the early signal, the intervention, and the follow-through after the meeting. Interviewers are scoring whether you protect both the decision quality and the two humans, in that order of attention but not of importance.
A strong answer
Catch it early, at the shift from technical to personal. Notice when claims stop being about the system ("this adds a write path we cannot scale") and start being about people ("you always design for imaginary scale"). The earlier you intervene, the cheaper the intervention.
Name the dynamic, blamelessly. Something plain: "We have moved from comparing designs to debating each other. Let me put this back on the table." Naming it out loud works because everyone felt it and nobody said it; the person who says it releases the room. No finger-pointing at either engineer; the goal is a reset, not a verdict.
Convert heat into criteria. Personal argument survives because the dispute is unbounded opinion. Force it onto shared ground:
| Question | Forces |
|---|---|
| What would each option cost to run at 10x current traffic? | Numbers instead of adjectives |
| Which option fails first under our top failure scenario? | Concrete reasoning |
| Migration effort per team, honestly? | Ownership stakes surface |
| What evidence would change your mind? | Falsifiability replaces stubbornness |
The last question asks for a decision criterion: asking a heated engineer "what would change your mind?" reframes them as reasonable by definition, since they must now describe evidence rather than defend identity. If the positions differ on a testable assumption, assign the benchmark or cost check. They may instead reflect different priorities, which require an explicit decision owner.
Park it if it will not resolve live. Forcing closure in a hot meeting produces a bad decision and lingering resentment. The parking motion has three parts, all stated: what remains open (one specific question), who resolves it (named owner, often one of the arguers, paired if trust needs rebuilding), and when it returns (next review, date certain). Then move the agenda. A parked disagreement with an owner is progress; an unresolved one that just runs out of clock is how teams learn to dread reviews.
Follow up privately, same day. A short message to each engineer: no adjudication, just "strong opinions today; here is what I need from us next time". Stop mocking, harassment or personal attacks in the meeting so the boundary is visible. Follow up privately with specific behavioral feedback and use the appropriate management or reporting process for serious conduct.
What interviewers probe next
"What if the senior-most person is the problem?" Same structure, more nerve: the criteria-forcing move works precisely because it is impersonal, giving status a graceful exit. If patterns persist, that is a manager conversation, not a facilitation one.
"Should juniors even be in this meeting?" Yes, and their silence during a shouting match is information. Asking a junior directly ("Priya, you built the prototype: what did you see?") both surfaces data and signals whose review this is.
"When do you kill the design entirely?" When the fight revealed the proposal lacks an owner for its operational burden rather than lacking a consensus. Some arguments are the review doing its job.
Common mistakes
Refereeing to a winner. Picking sides converts a design dispute into a politics problem and teaches the room that reviews are contests.
Letting it burn out on its own. Silence after a personal clash teaches everyone that reviews are unsafe, and juniors stop bringing hard questions exactly where they are most needed.
Handling it entirely offline afterwards. Private repair matters, but the meeting itself saw the behaviour and needs to see the correction, or the norm stays broken.