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System designMedium
Question
Design the integrity-and-safety gate for a file-upload service where every uploaded file (docs, images, archives, executables) must be checksum-verified end-to-end and scanned for malware BEFORE it becomes downloadable to other users, at 30K uploads/sec. Scanning is slow and bursty (some files take seconds, archives must be unpacked and scanned recursively). The uploader should get a fast 'received' ack, but the file must not be shareable until it clears, and a verdict can change later when virus signatures update.
What a strong answer looks like
Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.
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