What it is
Edge runtime ran your serverless functions at CDN PoPs — Cloudflare's network, Vercel's network, AWS Lambda@Edge. Cold starts in milliseconds because the V8 isolate was pre-warmed. Geographically distributed by default.
What changed in 2025
Vercel's Edge Functions had real compatibility issues: many npm packages don't run on edge (no native Node APIs), the V8-isolate sandbox is strict, debugging is harder. Vercel deprecated dedicated Edge in favor of Fluid Compute — which runs full Node.js with similar cold-start characteristics and broader package support.
Cloudflare Workers and other true-edge platforms still exist. Specific use cases (auth checks at the edge, A/B test header rewrites, geolocation) still benefit from running there. General app code mostly doesn't.
When to use edge
- Middleware that needs to run before cache (auth checks, redirects, A/B variant selection)
- Geolocation-aware responses
- Header rewrites and request shaping
- Anything latency-critical where a few extra ms matters
When NOT to use edge
- Anything that calls a database in a single region (you negate the edge benefit by making a cross-region DB call)
- Anything that needs Node.js native APIs (large npm ecosystem)
- Complex business logic where debugging matters
What we use
For middleware (bot detection, geo headers): edge. For everything else (API routes, page rendering): Vercel Fluid Compute, which is regular Node.js with similar cold-start performance.
