Facebook cost-per-new-user estimate, production database move plan, LinkedIn home revamp

An interviewer asks three unrelated questions in a row: an estimate, a technical execution question and a product improvement question. Answer each one in turn. ### Clarifying Questions - For the estimate, does "customer" mean a person who starts using Facebook, or a business that starts advertising on it? - For the migration, what is moving, how large is the data, and how much downtime would the business accept? - For LinkedIn, is the home page the feed members see after signing in, or the page a signed-out visitor lands on? ### Part 1 — Estimate Facebook's cost to acquire a new customer Estimate how much it costs Facebook to acquire one new customer. ```hint Write the ratio first Define the numerator and the denominator before choosing any numbers, then split the denominator by the ways new people actually arrive. ``` #### What This Part Should Cover - A precise definition of a new customer and of which costs count as acquisition - An equation broken into channels, with every number labeled as an assumption and the arithmetic shown - A sanity check against a known reference point ### Part 2 — Run a database migration How would you carry out a database migration for a product that people are actively using? ```hint Plan the way back Before planning the move forward, decide how you would prove the new database is correct and how you would switch back if it is not. ``` #### What This Part Should Cover - Scoping: the reason for the move, the systems that depend on the data, and the downtime budget - A phased plan with verification at each step and a tested rollback path - How risk, timing and communication are managed from the PM's seat ### Part 3 — Improve LinkedIn's home page How would you improve LinkedIn's home page? ```hint Pick one member Job seekers, recruiters, creators and people who check in only occasionally want different things from the same page. Choose the group that matters most to the goal you set. ``` #### What This Part Should Cover - A goal for the home page tied to how LinkedIn creates value, and one chosen member segment - Specific pain points for that segment and a short, prioritized list of solutions - A success metric with guardrails ### What a Strong Answer Covers - Asking the one clarifying question each prompt needs, then committing to an interpretation - A complete, structured answer to every Part within the time, rather than depth on one and a rushed rest - Clear separation of assumptions from facts throughout - Each answer tied back to an outcome for customers or the business ### Follow-up Questions - How would your acquisition cost estimate differ for a new user in the United States compared with one in a fast-growing emerging market? - During the migration, the old and new databases disagree on a small share of records. What do you do before going further? - Your home page change raises feed engagement, but fewer members apply to jobs. How do you decide whether to ship it?