Your question is Social Platform Design at Scale. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Design a social media platform similar to a very popular existing one (scaling, DB schema, API design; asked about sharding; requirement was ~10,000 MAU). Asked in the Onsite round 3 stage.
Explain the core entities, APIs, storage choices, access patterns, and sharding strategy. Address how the design could support an ML-ranked feed without coupling feed generation to transactional writes. Discuss availability, consistency, pagination, observability, and graceful degradation. State assumptions explicitly and identify which decisions would change at larger scale.