mediumSystem Design

What is a CDN and how does it work?

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01

Understand the problem

Explain content delivery networks.

cdn
02

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04

Read the code

Cache-Control headers (origin response)
// Static, versioned asset (filename has a content hash) -> cache forever:
Cache-Control: public, max-age=31536000, immutable

// HTML that may change -> let the CDN serve stale briefly while refreshing:
Cache-Control: public, max-age=0, s-maxage=60, stale-while-revalidate=300

// Per-user / private data -> never cache at the shared edge:
Cache-Control: private, no-store
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