Facebook News Feed Photo Density: Finding the Optimal Amount with Metrics and Experiments

Facebook's News Feed shows a mix of content types. As the product manager, you are asked to work out the right number of photos to show in the feed. Explain how you would arrive at that number. ```hint A number needs a goal There is no right number until "right" is defined. Decide what the feed should achieve and what you refuse to sacrifice, then think about how real behavior could reveal the number instead of you guessing it. ``` ### Clarifying Questions - Does "number of photos" mean how often photo posts appear among the stories in a session, or how many images a single multi-photo post shows before the viewer taps in? - Should the result be one number for everyone, or may it vary by person and context? - Which surfaces are in scope: the mobile app, the desktop site, or both? - What prompted the question now: falling engagement with photo posts, a push toward another format, or complaints about a cluttered feed? ### What a Strong Answer Covers - A goal tied to what the feed is for, plus a primary metric and guardrails that would expose the cost of both too many and too few photos. - The trade-offs of photo density for viewers, for the people who post photos, and for other content types, ads included. - A sound experiment design: variants, unit of randomization, duration, novelty effects and spillover onto the people who post. - Turning results into a decision, including the chance that the best amount differs by segment and that a ranking rule beats a fixed quota. ### Follow-up Questions - The photo-heaviest variant wins on time spent, but people write fewer text posts afterwards. What do you ship? - How would you tell whether a two-week result will still hold six months later? - If you replace the fixed number with a ranking model, how do you keep it from flooding feeds with photos?