Instagram has noticed that overall user engagement (likes, comments, posts, stories, time-in-feed) has plateaued and is beginning to decline in some key cohorts. You are the PM in charge of "Engagement" and have been asked to reverse this trend. Walk the interviewer through how you would:
Diagnose why engagement is slipping—form hypotheses, pick metrics, and identify the user segments most affected.
Prioritise the root-cause problems you want to solve first.
Generate and evaluate concrete product ideas (features, tooling, ranking, incentives, etc.) that could measurably lift engagement again.
Define the experiments you would run, what success metrics you would track, and how you would decide whether to ship, iterate, or kill each idea.
Assume no engineering constraints for early brainstorming, but be ready to discuss trade-offs, effort, and long-term sustainability.