- name
- edge-computing
- description
- Edge computing with Cloudflare Workers, Deno Deploy, Bun, Vercel Edge Functions, AWS Lambda@Edge, and edge databases (Turso, D1, DynamoDB Global Tables). Use when building low-latency edge applications, edge-side rendering, or globally distributed compute.
Edge Computing
Platforms
| Platform | Runtime | Cold Start | Limits |
|---|
| Cloudflare Workers | V8 isolates | ~0ms | 128MB, 30s CPU |
| Deno Deploy | V8 isolates | ~0ms | 512MB, 50ms CPU |
| Vercel Edge Functions | V8 isolates | ~0ms | 128MB, 25s |
| AWS Lambda@Edge | Node.js | ~100ms | 128MB, 5s (viewer) |
| Bun | JavaScriptCore | N/A (server) | No hard limits |
Cloudflare Workers
export default {
async fetch(request: Request, env: Env): Promise<Response> {
const url = new URL(request.url);
// KV storage
const cached = await env.KV.get(url.pathname);
if (cached) return new Response(cached, { headers: { 'Cache-Control': 'max-age=60' } });
// D1 database
const { results } = await env.DB.prepare('SELECT * FROM users WHERE id = ?')
.bind(url.searchParams.get('id'))
.all();
// Durable Objects for state
const id = env.COUNTER.idFromName('global');
const obj = env.COUNTER.get(id);
const count = await obj.fetch(request);
return new Response(JSON.stringify(results));
}
};
Edge Databases
| Database | Type | Best For |
|---|
| Cloudflare D1 | SQLite | Workers-native, SQL at edge |
| Turso | libSQL (SQLite) | Multi-region replicas, embedded |
| Cloudflare KV | Key-value | Simple caching, config |
| Durable Objects | Stateful | Real-time, coordination, counters |
| Upstash Redis | Redis | Rate limiting, sessions at edge |
Deno Deploy
Deno.serve(async (req: Request) => {
const kv = await Deno.openKv();
const url = new URL(req.url);
if (req.method === "POST") {
const body = await req.json();
await kv.set(["items", crypto.randomUUID()], body);
return new Response("Created", { status: 201 });
}
const entries = kv.list({ prefix: ["items"] });
const items = [];
for await (const entry of entries) items.push(entry.value);
return Response.json(items);
});
Patterns
- Edge-side rendering: SSR at the edge for <50ms TTFB globally
- Smart routing: Geo-aware request routing based on
request.cf.country - Edge caching: Cache API for fine-grained control, stale-while-revalidate
- Rate limiting: Sliding window counters with Durable Objects or Upstash
- A/B testing: Edge-side feature flags without origin round-trips
- Image optimization: On-the-fly transforms at edge (Cloudflare Images, Imgproxy)
Constraints & Gotchas
- No Node.js APIs (fs, net, etc.) in V8 isolate runtimes
- No native modules or binaries (use WASM for compute-heavy work)
- Limited CPU time per request — offload heavy work to queues
- Cold starts are near-zero for isolates but real for Lambda@Edge
- Database connections: use HTTP-based clients, not TCP connection pools
