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Chapter 1: What Edge Computing Is and Where the Edge Lives
The edge is not a place; it is a latency budget. For interactive applications, the round-trip budget between a user gesture and a visible response is 100 milliseconds — anything longer and the user perceives the system as sluggish. The traditional centralized cloud model, with round trips of 50 to 200 milliseconds to the nearest region, leaves almost no headroom inside that budget once you account for the application logic itself.
Where the edge actually sits
Three practical tiers exist for edge infrastructure:
1. CDN edge nodes — Cloudflare, Fastly, Akamai. ~50ms from most users. Best for HTTP request/response, JWT verification, A/B routing, and stateless transforms. 2. Regional points of presence — AWS Local Zones, Azure Edge Zones. ~20-30m
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Chapter 2: Deployment Patterns That Actually Work
Once you accept that edge means trading per-CPU cost for latency, the next question is which deployment pattern fits your workload. There are three that account for 90 percent of production edge systems: CDN functions, regional PoPs, and device-edge orchestration.
CDN functions
The dominant pattern for 2025. Cloudflare Workers, Fastly Compute, Deno Deploy. Run JavaScript or WASM at hundreds of POPs. The pattern works for:
- Auth token verification
- Request routing and A/B testing
- Geo-aware redirects
- Image transformation
- Short-lived stateful flows (a few seconds max)
What does not work on CDN functions: long-lived TCP connections, large memory footprints, anything that needs more than 128MB of RAM.
The reference architecture is to keep your application origin in a single region and use CDN functions as a smart reverse proxy. State stays where it has always lived; the edge becomes a fast first hop.
Regional PoPs
For applications that need a real database read on the hot path, regional PoPs are the answer. AWS Local Zones, Azure Edge Zones, and Google Distributed Cloud all offer this. The pa
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