Imported from personamanagmentlayer/pcl (stdlib/cloud/cloudflare-expert/SKILL.md). Install upstream with npx skills add personamanagmentlayer/pcl --skill cloudflare-expert. Copyright stays with the author.

Cloudflare Expert

Expert guidance for Cloudflare Workers, edge computing, CDN optimization, and Cloudflare security services.

Core Concepts

Cloudflare Services

• Cloudflare Workers (serverless edge computing)
• CDN and caching
• DDoS protection
• Web Application Firewall (WAF)
• DNS management
• Load balancing
• Workers KV (key-value storage)
• Durable Objects

Edge Computing

• Deploy code globally
• Reduce latency
• Process at the edge
• Distributed state
• Real-time applications

Developer Tools

• Wrangler CLI
• Workers Playground
• Edge APIs
• Analytics and logs

Cloudflare Workers

// Basic Worker
export default {
  async fetch(request, env, ctx) {
    return new Response('Hello from Cloudflare Workers!', {
      headers: { 'Content-Type': 'text/plain' }
    });
  }
};

// Advanced routing
export default {
  async fetch(request, env, ctx) {
    const url = new URL(request.url);

    // Route based on path
    switch (url.pathname) {
      case '/api/users':
        return handleUsers(request, env);
      case '/api/posts':
        return handlePosts(request, env);
      default:
        return new Response('Not Found', { status: 404 });
    }
  }
};

// API endpoint with JSON
async function handleUsers(request, env) {
  if (request.method === 'GET') {
    const users = await env.USERS_KV.get('users', { type: 'json' });
    return new Response(JSON.stringify(users), {
      headers: { 'Content-Type': 'application/json' }
    });
  }

  if (request.method === 'POST') {
    const body = await request.json();
    await env.USERS_KV.put('users', JSON.stringify(body));
    return new Response('Created', { status: 201 });
  }

  return new Response('Method Not Allowed', { status: 405 });
}

Workers KV Storage

// Workers KV operations
export default {
  async fetch(request, env, ctx) {
    // Write
    await env.MY_KV.put('key', 'value');

    // Write with metadata and expiration
    await env.MY_KV.put('key', 'value', {
      metadata: { userId: '123' },
      expirationTtl: 3600 // 1 hour
    });

    // Read
    const value = await env.MY_KV.get('key');

    // Read as JSON
    const jsonValue = await env.MY_KV.get('key', { type: 'json' });

    // Read with metadata
    const { value, metadata } = await env.MY_KV.getWithMetadata('key');

    // Delete
    await env.MY_KV.delete('key');

    // List keys
    const keys = await env.MY_KV.list({ prefix: 'user:' });

    return new Response(JSON.stringify({ value, keys }));
  }
};

// Caching pattern
class CachedAPI {
  constructor(kv) {
    this.kv = kv;
  }

  async get(key, fetcher, ttl = 3600) {
    // Try cache first
    const cached = await this.kv.get(key, { type: 'json' });
    if (cached) return cached;

    // Fetch and cache
    const data = await fetcher();
    await this.kv.put(key, JSON.stringify(data), {
      expirationTtl: ttl
    });

    return data;
  }
}

export default {
  async fetch(request, env, ctx) {
    const cache = new CachedAPI(env.MY_KV);

    const data = await cache.get('api:users', async () => {
      const response = await fetch('https://api.example.com/users');
      return response.json();
    }, 3600);

    return new Response(JSON.stringify(data));
  }
};

Caching Strategies

// Cache API
async function cacheFirst(request) {
  const cache = caches.default;
  let response = await cache.match(request);

  if (!response) {
    response = await fetch(request);
    // Cache for 1 hour
    response = new Response(response.body, response);
    response.headers.set('Cache-Control', 'max-age=3600');
    await cache.put(request, response.clone());
  }

  return response;
}

// Stale-while-revalidate
async function staleWhileRevalidate(request, ctx) {
  const cache = caches.default;
  let response = await cache.match(request);

  // Background refresh
  ctx.waitUntil(
    fetch(request).then((freshResponse) => {
      const clonedResponse = freshResponse.clone();
      cache.put(request, clonedResponse);
    })
  );

  if (response) {
    return response;
  }

  return fetch(request);
}

// Custom cache keys
function customCacheKey(request) {
  const url = new URL(request.url);

  // Ignore query parameters for caching
  url.search = '';

  // Add custom cache key based on headers
  const userAgent = request.headers.get('User-Agent');
  const isMobile = /mobile/i.test(userAgent);
  url.searchParams.set('device', isMobile ? 'mobile' : 'desktop');

  return new Request(url.toString(), request);
}

export default {
  async fetch(request, env, ctx) {
    const cacheKey = customCacheKey(request);

    if (request.url.includes('/api/')) {
      // API routes: stale-while-revalidate
      return staleWhileRevalidate(cacheKey, ctx);
    }

    // Static assets: cache first
    return cacheFirst(cacheKey);
  },
};

Edge Functions

// HTML rewriting
export default {
  async fetch(request, env, ctx) {
    const response = await fetch(request);

    // Inject analytics script
    return new HTMLRewriter()
      .on('head', new HeadInjector())
      .transform(response);
  }
};

class HeadInjector {
  element(element) {
    element.append(
      '<script>console.log("Injected at edge!");</script>',
      { html: true }
    );
  }
}

// Geolocation-based routing
export default {
  async fetch(request, env, ctx) {
    const country = request.cf.country;

    // Route based on country
    const apiEndpoint = {
      'US': 'https://us-api.example.com',
      'EU': 'https://eu-api.example.com',
      'default': 'https://global-api.example.com'
    }[country] || 'https://global-api.example.com';

    const url = new URL(request.url);
    const apiUrl = new URL(url.pathname, apiEndpoint);

    return fetch(apiUrl, request);
  }
};

// A/B testing
export default {
  async fetch(request, env, ctx) {
    const url = new URL(request.url);

    // Determine variant
    let variant = request.headers.get('Cookie')?.match(/variant=(\w+)/)?.[1];

    if (!variant) {
      variant = Math.random() < 0.5 ? 'A' : 'B';
    }

    // Fetch appropriate version
    const response = await fetch(`${url.origin}/variant-${variant}${url.pathname}`);

    // Set cookie
    const newResponse = new Response(response.body, response);
    newResponse.headers.set('Set-Cookie', `variant=${variant}; Path=/; Max-Age=86400`);

    return newResponse;
  }
};

Wrangler CLI

# Initialize project
wrangler init my-worker

# Development server
wrangler dev

# Deploy to production
wrangler publish

# Deploy to specific environment
wrangler publish --env production

# Tail logs
wrangler tail

# KV operations
wrangler kv:namespace create "MY_KV"
wrangler kv:key put --namespace-id=<id> "key" "value"
wrangler kv:key get --namespace-id=<id> "key"

# Durable Objects
wrangler publish --new-class Counter

# Secrets
wrangler secret put SECRET_NAME

wrangler.toml Configuration

name = "my-worker"
main = "src/index.js"
compatibility_date = "2024-01-01"

# KV bindings
kv_namespaces = [
  { binding = "MY_KV", id = "xxxxxxxx" },
  { binding = "CACHE_KV", id = "yyyyyyyy" }
]

# Durable Objects
[durable_objects]
bindings = [
  { name = "COUNTER", class_name = "Counter" },
  { name = "CHAT_ROOM", class_name = "ChatRoom" }
]

[[migrations]]
tag = "v1"
new_classes = ["Counter", "ChatRoom"]

# Environment variables
[vars]
ENVIRONMENT = "production"

# Routes
routes = [
  { pattern = "example.com/*", zone_name = "example.com" }
]

# Cron triggers
[triggers]
crons = ["0 */6 * * *"]

Best Practices

Performance

• Cache aggressively at the edge
• Minimize worker execution time
• Use Workers KV for global data
• Implement connection pooling
• Optimize cache keys
• Use stale-while-revalidate
• Minimize external requests

Security

• Validate all inputs
• Implement rate limiting
• Use secrets for sensitive data
• Set security headers
• Implement CORS properly
• Use HTTPS everywhere
• Log security events

Development

• Use TypeScript for type safety
• Test locally with wrangler dev
• Implement proper error handling
• Monitor worker metrics
• Use environment variables
• Version your workers
• Document API endpoints

Anti-Patterns

❌ Storing large data in KV frequently ❌ Long-running computations in workers ❌ Not implementing caching ❌ Hardcoding secrets ❌ Ignoring rate limits ❌ No error handling ❌ Excessive external API calls

Reference Documentation

Detailed material lives alongside this skill and is read on demand:

• Request/Response Handling
• Durable Objects

Resources

• Cloudflare Workers: https://workers.cloudflare.com/
• Wrangler CLI: https://developers.cloudflare.com/workers/wrangler/
• Workers Examples: https://developers.cloudflare.com/workers/examples/
• Durable Objects: https://developers.cloudflare.com/workers/learning/using-durable-objects/
• Workers KV: https://developers.cloudflare.com/workers/runtime-apis/kv/