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HLD Learn/Global-Scale Architecture
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Edge Computing

4 min read

You'll learn to

  • -Explain what runs at the edge beyond simple caching

The CDN chapter back in Module 1 described edge locations purely as caches: serve a static file from nearby instead of round-tripping to the origin. Edge computing takes the same geographic idea and adds real computation to it: what if the edge could run actual code, not just serve cached bytes?

From Caching to Compute

Edge functions (Cloudflare Workers, AWS Lambda@Edge) let you run JavaScript or similar code at hundreds of edge locations worldwide: handling authentication checks, A/B test assignment, header rewriting, or simple personalization before a request ever reaches your origin servers. For a globally distributed user base, this can cut tail latency dramatically, because only genuine cache misses ever need to travel all the way to a single origin region.

Client
Edge Function
Origin

An edge function handles cheap, stateless checks (auth, A/B routing) close to the user; only genuine cache misses and heavier logic travel all the way to the origin.

Edge FunctionOrigin- only when genuinely needed

The trade-off is real: edge runtimes are deliberately constrained (limited CPU time, limited memory, restricted APIs), so only logic that's genuinely cheap and stateless belongs there; anything heavier still belongs in the origin region.

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Ready to Build This?

Level 42 (CDN Design) and Level 65 (Global CDN & Edge Computing Platform) are this module's exercises.