How do you decide between a before-save and an after-save record-triggered flow?

If I only need to update fields on the record that triggered the flow, I use a before-save flow optimized for Fast Field Updates. It is faster because it changes the record before it is saved and does not require an extra update.

If I need to create or update related records, send emails, call subflows or use other actions, I use an after-save flow optimized for Actions and Related Records, because those need the record to be committed and to have an ID.

The interviewer checks whether the candidate understands the performance difference and the capability limits of before-save flows. Mentioning entry conditions to avoid unnecessary runs is a plus. A pitfall is using after-save flows for simple same-record field updates.