Edge Function

Edge functions run in a lightweight V8 isolate (Cloudflare Workers, Vercel Edge, Netlify Edge) or a Deno runtime (Deno Deploy, Netlify Edge), placed at hundreds of CDN locations worldwide. Time-to-first-byte is typically 50-150 ms anywhere , much faster than a single-region Lambda. Trade-off: edge runtimes restrict what your code can do. No native Node modules. No filesystem. Limited memory and execution time. Web-standard APIs (fetch, Web Streams, Web Crypto) are available; npm packages with C/native dependencies are not. When edge wins: cookie-based personalization, A/B testing, redirect rules, lightweight data fetching from a global database. When edge loses: anything needing a Node module like Sharp, Puppeteer, native binaries, or long-running workloads. Cloudflare Workers gives 100,000 free requests per day bundled with Pages. Vercel Edge gives 100 GB-hours of execution on Hobby. Netlify Edge gives 100 GB-hours. Deno Deploy gives 1 million requests per month. The free tiers are generous because edge compute is cheap to host , runs are measured in milliseconds.