Regularly prune your backlog. If an item has sat untouched for six months, either prioritise it or delete it. A bloated backlog is not a roadmap - it is a graveyard of good intentions.
Strong answers describe a regular cadence: grooming sessions with engineering, pruning stale items, adding acceptance criteria, splitting large stories, and ensuring the top of the backlog is always sprint-ready. Best candidates mention the danger of an ever-growing backlog full of items nobody will ever build.
Tests execution discipline. PMs with messy backlogs waste team time in planning sessions. Those who maintain a clean, prioritised backlog enable smooth sprint planning and honest stakeholder communication.