Your customer urgently needs a feature. Your own product team has looked at it and said no. Resolve it.

The reason this is asked is that all three obvious answers are disqualifying, and candidates reach for them in a predictable order: promise it and sort it out later, tell the customer product said no, or quietly fork the thing and build it. The last is the most seductive because it works this quarter and it is how field teams end up maintaining a shadow product they can never upgrade. Strong candidates do two things first: separate the requested solution from the underlying need, and find out WHY product declined, because a no based on 'only one customer wants this' and a no based on 'this conflicts with the data model' need completely different responses.