Answer "why didn't you use X?" with your reasons, not defensiveness

"Why didn't you use Flutter / MongoDB / a transformer model / microservices?" is one of the most common questions. It is not an accusation; it checks whether your choices were deliberate.

A strong answer has three parts:

1. What you needed: "We needed offline storage with relational queries on low-end phones."
2. Why your choice fit: "SQLite through React Native met that, and two of us already knew React."
3. When X would be better: "If we needed to share most code with a web app built in Dart, or if no one knew React, Flutter would be a strong choice."

If you genuinely did not consider X, say so honestly and reason about it on the spot. The design decisions table in your report is your best preparation for these questions.