System Design

Content Delivery Network (CDN)

System DesignPerformanceNetwork

A distributed group of servers that caches content near end users.

Core Concepts

⚡

Edge Servers

Servers strategically placed at the network edge, closer to users than the origin server.

🏢

Origin Server

The 'Master' server where the original content lives. CDNs pull from here on cache miss.

📍

PoP (Points of Presence)

Physical locations where CDN servers reside. More PoPs = lower latency globally.

⏱️

TTFB Reduction

Time To First Byte is drastically reduced because data travels a shorter distance.

Simulation: Cache Check

See the difference between a Cache Miss vs Cache Hit

User

MISS

CDN Edge

Origin

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Architecture Flow

How a CDN sits between users and your server

sequenceDiagram participant User participant Edge as CDN Edge participant Origin as Origin Server User->>Edge: Request Content alt Cache Miss Edge->>Origin: Fetch Content Origin-->>Edge: Return Data Edge->>Edge: Cache Data else Cache Hit Edge->>Edge: Retrieve from Cache end Edge-->>User: Return Content

CDN vs Direct Origin

Feature	With CDN	Direct Origin
Latency	Low (Served from Edge)	High (Depends on distance)
Bandwidth Costs	Lower (Offloads origin)	Higher (Origin handles all)
Reliability	High (Redundant nodes)	Single point of failure
Security	DDoS Protection included	Requires separate firewall
Scalability	Instant (Global network)	Vertical scaling limits

Guide Contributors

ObydulSenior Software Engineer

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