Design large video upload for a YouTube-like app

Q: Design large video upload for a YouTube-like app

This is a System Design interview question from Coupang for Software Engineer roles. View the full question and solution on PracHub.

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Question

System Design Prompt

Design the video upload subsystem for a YouTube-like product that supports large video files.

Core user flow

User selects a large video file (hundreds of MB to tens of GB).
Upload should be reliable (resume after network drops).
After upload, the platform processes the video (e.g., transcode) and eventually makes it playable.

Requirements

Support resumable uploads and unstable mobile networks.
Efficiently handle large files (chunking, retries, integrity checks).
Provide upload status to clients (progress, failure reasons).
Ensure uploaded content is durable and not lost.
Basic security: authenticate users, authorize uploads, prevent misuse.

Scale assumptions (state your own if needed)

Millions of users
Spiky traffic (new releases)
Global uploads

Deliverables

APIs, data model, and high-level architecture
Storage strategy for raw uploads and processed outputs
Processing pipeline (transcoding, thumbnails)
Failure handling, idempotency, and observability
Key trade-offs