Design a Global Content Delivery Network for Videos
Last updated: March 3, 2025
Quick Overview
Design CDN architecture for multi-region video delivery: PoP placement, cache eviction, origin shielding, and cost versus latency trade-offs.
ByteDance
System Design
Software Engineer
ByteDance
March 3, 2025Software Engineer
System Design Round
System Design
Hard
5
12
4,091 solved
Design CDN architecture for multi-region video delivery: PoP placement, cache eviction, origin shielding, and cost versus latency trade-offs.
Infrastructure-focused question testing deep understanding of content delivery at TikTok's global scale.
What the Interviewer Expects
- Design PoP placement strategy based on user density
- Implement intelligent cache eviction policies
- Address origin shielding and request collapsing
- Optimize cost versus latency trade-offs
- Handle cache invalidation for content policy violations
Key Topics to Cover
CDN architecture
Cache eviction
Origin shielding
Edge computing
Content delivery economics
How to Approach This
- Start by clarifying functional and non-functional requirements with the interviewer.
- Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
- Draw a high-level architecture first, then deep dive into 1-2 critical components.
- Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
- Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
- How do you measure CDN effectiveness?
- What is your strategy for emerging markets with poor connectivity?
- How do you handle content takedowns across all PoPs?
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Practice System Design ProblemsSample Answer
Requirements
- Functional Requirements:
- Users can stream HD videos with minimal latency.
- Intelligent cache eviction policies to ensure popular content remains cached.
- Origin shielding to reduce loa...
Capacity Estimation
- User Base: Assume 1 billion DAUs (Daily Active Users).
- Video Consumption: Average user consumes 1 hour of video daily.
- Video Size: Average video bitrate is 5 Mbps.
- **Data Transfer ...
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