if (url.pathname === "/api/hello") {
  return Response.json({ message: "Hello from the edge!" });
}

return new Response("Not found", { status: 404 });

}, };


## Core Concepts

### Workers with KV

```typescript
export interface Env {
  MY_KV: KVNamespace;
  MY_DO: DurableObjectNamespace;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // Read from KV
    const cached = await env.MY_KV.get("key", "json");
    if (cached) return Response.json(cached);

    // Fetch and cache
    const data = await fetchData();
    await env.MY_KV.put("key", JSON.stringify(data), {
      expirationTtl: 3600,
    });

    return Response.json(data);
  },
};

Durable Objects

export class Counter implements DurableObject {
  state: DurableObjectState;

  constructor(state: DurableObjectState) {
    this.state = state;
  }

  async fetch(request: Request): Promise<Response> {
    let count = (await this.state.storage.get<number>("count")) || 0;

    if (request.method === "POST") {
      count++;
      await this.state.storage.put("count", count);
    }

    return Response.json({ count });
  }
}

Common Patterns

Pages Deployment

# wrangler.toml
name = "my-app"
compatibility_date = "2024-01-01"

[site]
bucket = "./dist"

[[kv_namespaces]]
binding = "CACHE"
id = "abc123"

# Deploy
npx wrangler deploy

# Pages
npx wrangler pages deploy dist

Best Practices

Do:

Use KV for caching
Implement proper error handling
Use Durable Objects for state
Configure proper cache headers

Don't:

Block the event loop
Make too many subrequests
Store large data in KV values
Ignore execution time limits

Troubleshooting

Issue	Cause	Solution
CPU time exceeded	Long computation	Optimize or use DO
KV stale	Eventual consistency	Use metadata for freshness
CORS error	Missing headers	Add CORS headers

Durable Objects

Common Patterns

Pages Deployment

Best Practices

Troubleshooting

References

cloudflare

Cloudflare

When to Use

Quick Start

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