Cloudflare Workers Expert

Examples

Example 1: Basic Worker with KV Binding

export interface Env {
  MY_KV_NAMESPACE: KVNamespace;
}

export default {
  async fetch(
    request: Request,
    env: Env,
    ctx: ExecutionContext,
  ): Promise<Response> {
    const value = await env.MY_KV_NAMESPACE.get("my-key");
    if (!value) {
      return new Response("Not Found", { status: 404 });
    }
    return new Response(`Stored Value: ${value}`);
  },
};

Example 2: Edge Response Modification

export default {
  async fetch(request, env, ctx) {
    const response = await fetch(request);
    const newResponse = new Response(response.body, response);

    // Add security headers at the edge
    newResponse.headers.set("X-Content-Type-Options", "nosniff");
    newResponse.headers.set(
      "Content-Security-Policy",
      "upgrade-insecure-requests",
    );

    return newResponse;
  },
};

Best Practices

• ✅ Do: Use env.VAR_NAME for secrets and environment variables.
• ✅ Do: Use Response.redirect() for clean edge-side redirects.
• ✅ Do: Use wrangler tail for live production debugging.
• ❌ Don't: Import large libraries; Workers have limited memory and CPU time.
• ❌ Don't: Use Node.js specific libraries (like fs, path) unless using Node.js compatibility mode.

Troubleshooting

Problem: Request exceeded CPU time limit. Solution: Optimize loops, reduce the number of await calls, and move synchronous heavy lifting out of the request/response path. Use ctx.waitUntil() for tasks that don't block the response.

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.