System design interview question
"Design TikTok. Users open the app and immediately get an infinite feed of short videos chosen for them — no following required. They swipe, and the next video plays instantly. 1 billion users, 100 million videos uploaded per day."
recommendation-driven feed with zero social graph, plus an unusual client-side constraint — the next video must start playing with no perceptible load time. That prefetching requirement is the part candidates miss, and it changes the API shape.
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