edge-computing-patterns

# Edge Computing Patterns

## Overview

Edge computing runs code closer to users worldwide, reducing latency from seconds to milliseconds. This skill covers Cloudflare Workers, Vercel Edge Functions, and Deno Deploy patterns for building globally distributed applications.

**When to use this skill:**
- Global applications requiring <50ms latency
- Authentication/authorization at the edge
- A/B testing and feature flags
- Geo-routing and localization
- API rate limiting and DDoS protection
- Transforming responses (image optimization, HTML rewriting)

## Platform Comparison

| Feature | Cloudflare Workers | Vercel Edge | Deno Deploy |
|---------|-------------------|-------------|-------------|
| Cold Start | <1ms | <10ms | <10ms |
| Locations | 300+ | 100+ | 35+ |
| Runtime | V8 Isolates | V8 Isolates | Deno |
| Max Duration | 30s (paid: unlimited) | 25s | 50ms-5min |
| Free Tier | 100k req/day | 100k req/month | 100k req/month |

## Platform-Specific Implementation

For detailed code examples and patterns, load the appropriate reference file:

### Cloudflare Workers
**Reference:** `references/cloudflare-workers.md`
- Worker fetch handlers and routing
- KV storage patterns (eventually consistent)
- Durable Objects for stateful edge
- Wrangler CLI and wrangler.toml configuration
- Caching strategies with Cache API

### Vercel Edge Functions
**Reference:** `references/vercel-edge.md`
- Edge Middleware for Next.js (auth, A/B testing, geo-routing)
- Edge API routes with streaming
- Edge Config for feature flags
- Geolocation-based routing patterns

### Runtime Differences
**Reference:** `references/runtime-differences.md`
- Node.js APIs NOT available at edge
- Web API compatibility matrix
- Polyfill strategies for crypto, Buffer, streams

## Edge Runtime Constraints

**Available APIs:**
- fetch, Request, Response, Headers
- URL, URLSearchParams
- TextEncoder, TextDecoder
- ReadableStream, WritableStream
- crypto, SubtleCrypto (Web Crypto API)
- Web APIs (atob, btoa, setT