These are LLD questions of the kind Meta actually asks — the patterns reported from Meta's AI-engineering rounds, where design trade-offs, scale and failure modes matter as much as definitions. Treat this page as a mock interview: say every answer out loud before revealing it. If one surprises you, the lesson behind it is linked at the bottom.
Meta LLD concept questions
Meta's LLD rounds sometimes ask for a simplified news-feed ranking system where the ranking formula may change often. How would you design the ranking step?
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When a user posts, many followers' feeds need to be updated. What design pattern captures 'notify many dependents when one thing changes,' and what's the risk to watch for?
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Interviewer: 'now add the ability for a user to hide posts from a specific person, without changing how ranking or fan-out works.' Where does this fit?
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How to use this page: Meta rarely asks something you've never seen — they ask a standard LLD concept and then push one level deeper ("why?", "what would you do if..."). Master the concept in the LLD course lessons, and the follow-up stops being scary.
Keep practising: SOLID Principles, Strategy Pattern, Design a Parking Lot and UML Diagrams cover what most Meta LLD rounds test.