Edge Computing — Run Logic at the CDN Layer for Instant Response Times

Not every computation should run at the edge. Edge functions are constrained by execution time (CloudFront Functions: 1ms, Lambda@Edge: 5-30 seconds, Cloudflare Workers: 50ms CPU time), memory (2 MB for CloudFront Functions, 128 MB for Lambda@Edge, 128 MB for Workers), and network access (CloudFront Functions have no network access at all). The right use cases are lightweight, latency-sensitive operations that do not need database access.

Good edge use cases: URL rewriting and redirects (localized URLs, vanity URLs, legacy URL migration), header manipulation (adding security headers, setting cache control, CORS), authentication token validation (JWT verification without origin round-trip), A/B testing (routing users to different origins based on cookies), geolocation routing (serving region-specific content), and bot detection (blocking known bad actors before they reach your origin).

Bad edge use cases: Database queries, complex business logic, anything requiring more than a few milliseconds of computation, and operations that need access to your application's internal state. These should remain at the origin where they have full access to your infrastructure.

CloudFront Functions: For simple, high-volume operations (millions of requests per second) that need sub-millisecond execution. We implement URL normalization, redirect maps, cache key manipulation, and security header injection. CloudFront Functions run in the viewer request/response phases and execute in JavaScript with limited APIs — no network, no file system, just request/response manipulation.

Lambda@Edge: For operations that need network access or more compute time. We implement JWT validation (decode and verify tokens without calling the origin), dynamic origin selection (route to different backends based on request attributes), image resizing (fetch the original, resize at the edge, cache the result), and request enrichment (add user context headers before forwarding to the origin). Lambda@Edge runs in Node.js or Python and deploys to all CloudFront edge locations.

Cloudflare Workers: For teams on Cloudflare, Workers provide a V8 isolate runtime at every edge location. We implement API gateways (rate limiting, authentication, routing), full-page rendering (using Workers + KV or D1 for simple applications), and response transformation (HTML rewriting, API response modification). Workers support JavaScript, TypeScript, Rust (via WASM), and Python.

Testing and Deployment: Edge functions are tested locally using the provider's development tools (wrangler for Cloudflare, SAM for Lambda@Edge) and deployed via your CI/CD pipeline. We configure canary deployments for Lambda@Edge (deploy to one region first, then all) and staged rollouts for Workers. Monitoring includes invocation count, execution duration, error rate, and cold start frequency.

An edge computing implementation for your CDN:

• Edge function development — functions written and tested for your specific use cases
• Platform configuration — CloudFront Functions, Lambda@Edge, or Workers deployed to all edge locations
• Authentication at edge — JWT validation without origin round-trip
• A/B testing — cookie-based routing to experiment variants at the edge
• Geolocation routing — region-specific content and redirects
• Security headers — CSP, HSTS, X-Frame-Options injected at the edge
• CI/CD integration — edge functions deployed via your existing pipeline
• Monitoring — invocation metrics, error rates, and execution duration dashboards