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System Design at Fastly
System Design at Fastly
Fastly built a developer-first CDN organised around fewer, denser PoPs and a programmable edge — Compute@Edge runs WebAssembly with sub-millisecond cold starts, and instant-purge clears cache in around 150 ms. Interviews focus on edge computing, real-time cache invalidation, programmability at the edge, and how a software-defined CDN differs from a traditional appliance-based one.
1 guide available•Interview focus: Programmable edge, cache invalidation, edge compute (Wasm), and software-defined CDN architecture.
Fastly System Design Interview Guides
Nov 25, 2025•20 min•
hard
How to Design a Content Delivery Network (CDN) - Complete System Design Guide
Master CDN system design for your next big tech interview. Covers Anycast vs DNS-based routing, PoP architecture, multi-tier cache hierarchy, push vs pull CDNs,...
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