How do you decide whether a requirement should be built in Flow or in Apex?

I start with declarative tools because they are easier for admins to maintain. Flow handles most record automation, guided screens and simple integrations with invocable actions.

I choose Apex when the logic is complex, needs fine-grained error handling, must process very large volumes efficiently, or requires capabilities Flow does not offer. Often the best design combines both, for example a flow calling an invocable Apex method.

Interviewers want pragmatic judgment and awareness of maintainability for the whole team. A pitfall is dismissing Flow entirely or forcing highly complex logic into an unmaintainable flow.