Metrics question
Let’s say we want to figure out for any Facebook user, who their best friend is so we can prioritize showing their content in the News Feed. What product signals and metrics (max 5) would you use to determine who a user’s best friend is?
- Meta
- Metrics
- Medium
Practice this question out loud. An AI interviewer asks it, follows up like a real interviewer would, and scores your answer. Type or speak.
Start a mock interview on this question · Mock interview from a job description
What this question tests
Tests translating a vague closeness concept into measurable behavioral signals and prioritizing them for a ranking model.
How to approach it
- Clarify the goal: best friend should predict content the user wants to see first in News Feed, not just who they message most.
- List signal categories: messaging frequency and recency, profile visits, photo co-tags, comment or reaction reciprocity, mutual friend overlap.
- Pick the top 5 by signal density: weekly message count, message reciprocity, profile view frequency, photo co-tags, comment reciprocity rate.
- Weight recency higher than raw volume so a friendship that cooled off decays in the ranking.
- Validate with survey data (asking users directly who their best friend is) and check precision against the signal-based ranking.
What a strong answer includes
- Names concrete signals: 30-day message frequency, reciprocal comment or like ratio, co-tagged photos, birthday interactions, profile visits.
- Requires reciprocity to separate mutual closeness from one-way admiration, such as following a celebrity.
- Builds in signal decay so a best friend from years ago who stopped talking naturally drops in rank.
Common mistakes
- Treating most-messaged alone as the answer, ignoring reciprocity and recency.
- Ignoring the privacy sensitivity of using private message metadata for ranking.
Likely follow-up questions
- How would you validate that these signals actually predict engagement lift in News Feed?
- How would you handle a user with no strong signal at all, like a brand-new account?
More metrics questions
- How would you measure the success of Facebook Likes?Meta · Metrics · Medium
- How would you measure improvements made to Facebook messenger?Meta · Metrics · Easy
- Imagine you are the PM in charge of Reactions on Facebook - the new way to interact with posts by using “love”, “haha”, “wow”, “sad”, and “angry” reactions. What would success look like in terms of number of non-like reactions per post at launch and how do you come up with this? Would this number differ by reaction? Why or why not?Meta · Metrics · Hard
- You launched a new signup flow to encourage new users to add more profile information. A/B test results indicate that the % of people that added more information increased by 8%. However, 7 day retention decreased by 2%. What do you do?Google · Metrics · Hard
- Define the metrics for YouTube search.Google · Metrics · Medium
- You are the PM of Instagram app. The MAU has been constant but DAU has declined. What will you do?Meta · Metrics · Medium
More questions from Meta
Learn the skill behind it
Chapters of the AI PM course that teach what this question tests.
- Chapter 9: Prove it paid off: outcomes, economics, and pricing
- Chapter 2: Data fluency: SQL, logs, and reading the truth yourself
- Chapter 14: Get the job: the AI PM interview loop