EDGE FUNCTION

An edge function is server-side code that runs at a CDN edge location physically close to the visitor, instead of at a single origin server. Platforms like Cloudflare Workers, Vercel Edge Functions, Netlify Edge Functions and Deno Deploy run code in a lightweight V8 or Deno runtime at hundreds of points of presence worldwide, so a request never travels back to a central origin for simple personalisation, redirects, authentication checks, or A/B-test routing. The trade for that speed is a constrained runtime: edge functions cannot use the full Node.js API, are time-limited, and have small memory budgets compared with traditional serverless functions.

How it works

Edge functions execute on the same fleet of servers that serves cached content from a CDN. Code is typically deployed as small JavaScript or WebAssembly modules. Common use cases: rewriting URLs, injecting personalisation, checking auth tokens, geo-routing, image optimisation triggers.

Why it matters

For latency-sensitive logic (auth, A/B routing, edge personalisation), edge functions eliminate a round-trip to the origin and improve TTFB and Core Web Vitals globally. For heavy backend work, traditional serverless or a real server is still the better fit.

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