Cloudflare Workers Has a Free API That Runs Your Code in 300+ Cities Worldwide

#cloudflare #serverless #edge #javascript

Cloudflare Workers run JavaScript at the edge — 300+ data centers, sub-millisecond cold starts, and a powerful runtime API.

Workers: Zero Cold Start

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const url = new URL(request.url);

    if (url.pathname === "/api/data") {
      const data = await env.DB.prepare("SELECT * FROM products LIMIT 20").all();
      return Response.json(data.results);
    }

    if (url.pathname === "/api/scrape") {
      const { targetUrl } = await request.json();
      const html = await fetch(targetUrl).then(r => r.text());
      return Response.json({ length: html.length, preview: html.slice(0, 500) });
    }

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

D1: SQLite at the Edge

// wrangler.toml
// [[d1_databases]]
// binding = "DB"
// database_name = "scraping-db"

export default {
  async fetch(request, env) {
    // Parameterized queries
    const products = await env.DB
      .prepare("SELECT * FROM products WHERE price < ? ORDER BY scraped_at DESC")
      .bind(50)
      .all();

    // Batch operations
    const batch = await env.DB.batch([
      env.DB.prepare("INSERT INTO products (title, price) VALUES (?, ?)").bind("Widget", 29.99),
      env.DB.prepare("UPDATE stats SET total = total + 1"),
    ]);

    return Response.json(products.results);
  },
};

R2: S3-Compatible Object Storage

export default {
  async fetch(request, env) {
    const url = new URL(request.url);
    const key = url.pathname.slice(1);

    if (request.method === "PUT") {
      await env.BUCKET.put(key, request.body, {
        httpMetadata: { contentType: request.headers.get("content-type") },
      });
      return new Response("Uploaded");
    }

    if (request.method === "GET") {
      const object = await env.BUCKET.get(key);
      if (!object) return new Response("Not Found", { status: 404 });
      return new Response(object.body, {
        headers: { "content-type": object.httpMetadata?.contentType || "application/octet-stream" },
      });
    }
  },
};

KV: Global Key-Value Store

// Read (cached globally)
const value = await env.KV.get("config", "json");

// Write with TTL
await env.KV.put("cache:products", JSON.stringify(data), { expirationTtl: 3600 });

// List keys
const { keys } = await env.KV.list({ prefix: "cache:" });

Durable Objects: Stateful Edge

export class ScrapingSession {
  state: DurableObjectState;

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

  async fetch(request: Request) {
    const count = (await this.state.storage.get("count")) || 0;
    await this.state.storage.put("count", count + 1);
    return Response.json({ scrapeCount: count + 1 });
  }
}

Queues: Background Processing

export default {
  async fetch(request, env) {
    await env.SCRAPE_QUEUE.send({ url: "https://example.com", priority: "high" });
    return new Response("Queued");
  },

  async queue(batch, env) {
    for (const message of batch.messages) {
      const { url } = message.body;
      const result = await scrape(url);
      await env.DB.prepare("INSERT INTO results (url, data) VALUES (?, ?)").bind(url, JSON.stringify(result)).run();
      message.ack();
    }
  },
};