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Patterns
Handling Large Blobs
Learn about how to handle large blobs in your system design interview.
The Problem
If you've been studying for system design interviews, you already know that large files belong in blob storage like S3, not in databases. This separation lets storage scale independently from compute and keeps database performance snappy.
While blob storage solved the storage problem, it didn't solve the data transfer problem. The standard approach routes file bytes through your application servers. A client uploads a 2GB video, the API server receives it, then forwards it to blob storage. Same for downloads - blob storage sends to the API server, which forwards to the client. This works for small files, but breaks down as files get bigger.
Server as a Proxy
The Solution
Simple Direct Upload
Simple Direct Download
Resumable Uploads for Large Files
State Synchronization Challenges
Cloud Provider Terminology
When to Use in Interviews
Common interview scenarios
When NOT to use it in an interview
Common Deep Dives
"What if the upload fails at 99%?"
"How do you prevent abuse?"
"How do you handle metadata?"
"How do you ensure downloads are fast?"
Conclusion
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