---
title: "What is edge computing? Running code at the CDN edge — warmup.rocks Glossary"
description: "Edge computing runs your code at CDN locations near users: Cloudflare Workers, Fastly Compute, Lambda@Edge. What runs well at the edge, how it turns dynamic pages cacheable, and why edge caches still start cold."
canonical: https://warmup.rocks/glossary/edge-computing
---

# Edge computing

**Edge computing** means running your code at a CDN's [points of presence](https://warmup.rocks/glossary/point-of-presence) instead of (or in front of) a central origin server. Cloudflare Workers, Fastly Compute and CloudFront Functions/Lambda@Edge all follow the same idea: the request is handled milliseconds from the user, before it ever crosses an ocean to your infrastructure.

## What runs well at the edge

-   **Request rewriting** — redirects, A/B bucketing, header manipulation, geo-based routing, auth checks.
-   **Cache programmability** — normalizing [cache keys](https://warmup.rocks/glossary/cache-key), caching responses the CDN's default rules would skip, or serving different cached variants per segment. On Cloudflare this is the [Workers Cache API](https://warmup.rocks/blog/cloudflare-workers-cache-api).
-   **Assembling responses** — stitching cached fragments with small dynamic parts (personalized header, cart count) so the bulk of the page stays cacheable instead of going fully dynamic.
-   **Full applications** — increasingly, whole apps run at the edge with edge-hosted data (KV stores, D1, Durable Objects), collapsing the origin entirely.

## Why it matters for caching

Edge compute and edge caching solve the same problem from two sides. Caching makes repeated responses fast; edge code makes the _uncacheable_ parts fast — and, used well, it converts "dynamic" pages back into cacheable ones. The classic failure mode it fixes: one personalized element (a cookie, a currency switcher) forcing an entire page to bypass the cache. Move that element into edge code and the page returns to being a [cache hit](https://warmup.rocks/glossary/cache-hit-ratio) for everyone.

## The caveat: edge caches still start cold

Edge functions run everywhere instantly, but any cache they populate is still per-PoP: what a Worker caches in Frankfurt does nothing for Sydney. The economics of [eviction](https://warmup.rocks/glossary/cache-eviction) and cold starts apply unchanged — which is why edge-heavy architectures still benefit from [cache warming](https://warmup.rocks/blog/what-is-cache-warming) across regions. See how your edge responds per location with the [website speed test](https://warmup.rocks/website-speed-test).