System Design · Meta · Hard
Requirements Functional behavior: accept posts, build searchable indexes, and serve keyword searches by returning the top K matches ordered by relevance. Capacity targets: index about 10 billion posts, sustain roughly 10,000 peak queries per second, and keep p95 latency under 200 ms. Key design choices: Inverted index: map each term to a postings list containing post IDs, ordered by recency and score. Ranking: begin with TF-IDF or BM25, then add a learned-to-rank layer.…
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