Cloudflare Workers (cloudflare/workers-sdk)

Cloudflare Workers

https://github.com/cloudflare/workers-sdk
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The Cloudflare Workers SDK provides tools and libraries for deploying serverless code globally,...

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# Cloudflare Workers SDK

The Cloudflare Workers SDK is a comprehensive monorepo containing all the tools needed to build, test, and deploy serverless applications on Cloudflare's global network. The SDK provides a complete development experience from project creation to production deployment, with the core packages being Wrangler (CLI tool), Miniflare (local simulator), create-cloudflare (project scaffolding), and the Vite plugin for modern frontend integration.

The SDK enables developers to write JavaScript/TypeScript code that runs at the edge on Cloudflare's network, with access to powerful primitives like KV storage, Durable Objects, R2 object storage, D1 databases, Queues, and AI services. The local development experience powered by Miniflare uses the same `workerd` runtime as production, ensuring consistent behavior between development and deployment.

---

## Wrangler CLI - Initialize Project

Initialize a new Cloudflare Workers project with a basic configuration file and entry point.

```bash
# Create a new Worker project interactively
npx wrangler init my-worker

# Create with default settings (no prompts)
npx wrangler init my-worker -y

# The generated wrangler.jsonc configuration file
{
  "$schema": "node_modules/wrangler/config-schema.json",
  "name": "my-worker",
  "main": "./src/index.ts",
  "compatibility_date": "2024-01-01"
}
```

---

## Wrangler CLI - Local Development Server

Start a local development server with hot reloading and devtools support for rapid iteration.

```bash
# Start local development server
npx wrangler dev

# Start with specific entry point
npx wrangler dev src/index.ts

# Start on specific port with inspector
npx wrangler dev --port 8080 --inspector-port 9229

# Start with remote bindings (connects to real Cloudflare services)
npx wrangler dev --remote

# Start with local persistence for storage bindings
npx wrangler dev --persist-to .wrangler/state
```

---

## Wrangler CLI - Deploy Worker

Deploy a Worker to Cloudflare's global network with automatic bundling and optimization.

```bash
# Deploy the Worker defined in wrangler.jsonc
npx wrangler deploy

# Deploy specific script with custom name
npx wrangler deploy src/index.ts --name my-production-worker

# Deploy with environment variables
npx wrangler deploy --var API_KEY:secret123 --var DEBUG:true

# Deploy to specific environment
npx wrangler deploy --env production

# Deploy with compatibility flags
npx wrangler deploy --compatibility-date 2024-01-01 --compatibility-flag nodejs_compat
```

---

## Wrangler CLI - KV Namespace Management

Create and manage Workers KV namespaces for key-value storage at the edge.

```bash
# Create a new KV namespace
npx wrangler kv namespace create MY_KV
# Output: Created namespace "my-worker-MY_KV" with id "abc123..."

# List all KV namespaces
npx wrangler kv namespace list

# Put a value into KV
npx wrangler kv key put --namespace-id abc123 "user:1" '{"name":"John"}'

# Get a value from KV
npx wrangler kv key get --namespace-id abc123 "user:1"

# Bulk upload from JSON file
npx wrangler kv bulk put --namespace-id abc123 data.json

# Delete a key
npx wrangler kv key delete --namespace-id abc123 "user:1"
```

---

## Wrangler CLI - R2 Object Storage

Manage R2 buckets for S3-compatible object storage with zero egress fees.

```bash
# Create a new R2 bucket
npx wrangler r2 bucket create my-bucket

# List all R2 buckets
npx wrangler r2 bucket list

# Upload an object to R2
npx wrangler r2 object put my-bucket/images/photo.jpg --file ./photo.jpg

# Download an object from R2
npx wrangler r2 object get my-bucket/images/photo.jpg --file ./downloaded.jpg

# Delete an object
npx wrangler r2 object delete my-bucket/images/photo.jpg
```

---

## Wrangler CLI - D1 Database

Create and manage D1 SQLite databases for serverless SQL at the edge.

```bash
# Create a new D1 database
npx wrangler d1 create my-database
# Output: Created database "my-database" with id "abc123..."

# List all D1 databases
npx wrangler d1 list

# Execute SQL query
npx wrangler d1 execute my-database --command "SELECT * FROM users"

# Execute SQL from file
npx wrangler d1 execute my-database --file ./schema.sql

# Create a migration
npx wrangler d1 migrations create my-database create_users_table

# Apply migrations
npx wrangler d1 migrations apply my-database

# Export database
npx wrangler d1 export my-database --output backup.sql
```

---

## Wrangler Configuration File

Configure your Worker with bindings, routes, and build settings in wrangler.jsonc.

```jsonc
{
  "$schema": "node_modules/wrangler/config-schema.json",
  "name": "my-api-worker",
  "main": "./src/index.ts",
  "compatibility_date": "2024-01-01",
  "compatibility_flags": ["nodejs_compat"],

  // KV Namespaces
  "kv_namespaces": [
    { "binding": "MY_KV", "id": "abc123..." }
  ],

  // R2 Buckets
  "r2_buckets": [
    { "binding": "MY_BUCKET", "bucket_name": "my-bucket" }
  ],

  // D1 Databases
  "d1_databases": [
    { "binding": "DB", "database_name": "my-database", "database_id": "xyz789..." }
  ],

  // Durable Objects
  "durable_objects": {
    "bindings": [
      { "name": "COUNTER", "class_name": "Counter" }
    ]
  },

  // Environment Variables
  "vars": {
    "API_URL": "https://api.example.com",
    "DEBUG": "false"
  },

  // Cron Triggers
  "triggers": {
    "crons": ["0 * * * *", "0 0 * * *"]
  },

  // Static Assets
  "assets": {
    "directory": "./public"
  },

  // Routes
  "routes": [
    { "pattern": "api.example.com/*", "zone_name": "example.com" }
  ]
}
```

---

## Worker Entry Point - Fetch Handler

Create a basic Worker that handles HTTP requests with the modern ES modules format.

```typescript
// src/index.ts
export interface Env {
  MY_KV: KVNamespace;
  DB: D1Database;
  MY_BUCKET: R2Bucket;
  API_KEY: string;
}

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

    // Route handling
    if (url.pathname === "/api/users") {
      const users = await env.DB.prepare("SELECT * FROM users").all();
      return Response.json(users.results);
    }

    if (url.pathname.startsWith("/files/")) {
      const key = url.pathname.slice(7);
      const object = await env.MY_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" }
      });
    }

    // Cache API usage
    const cache = caches.default;
    const cached = await cache.match(request);
    if (cached) return cached;

    const response = new Response("Hello from Cloudflare Workers!");
    ctx.waitUntil(cache.put(request, response.clone()));
    return response;
  },

  // Scheduled handler for cron triggers
  async scheduled(controller: ScheduledController, env: Env, ctx: ExecutionContext) {
    console.log(`Cron triggered at ${controller.scheduledTime}`);
    // Perform scheduled tasks
  },
};
```

---

## Durable Objects

Create stateful serverless objects with strong consistency guarantees.

```typescript
// src/counter.ts
export class Counter implements DurableObject {
  private state: DurableObjectState;
  private value: number = 0;

  constructor(state: DurableObjectState, env: Env) {
    this.state = state;
    // Load persisted value on initialization
    this.state.blockConcurrencyWhile(async () => {
      this.value = (await this.state.storage.get<number>("value")) || 0;
    });
  }

  async fetch(request: Request): Promise<Response> {
    const url = new URL(request.url);

    if (url.pathname === "/increment") {
      this.value++;
      await this.state.storage.put("value", this.value);
      return Response.json({ value: this.value });
    }

    if (url.pathname === "/decrement") {
      this.value--;
      await this.state.storage.put("value", this.value);
      return Response.json({ value: this.value });
    }

    return Response.json({ value: this.value });
  }

  // Alarm handler for scheduled wake-ups
  async alarm(): Promise<void> {
    console.log("Alarm triggered!");
    // Perform cleanup or scheduled tasks
  }
}

// src/index.ts - Using Durable Objects
export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const id = env.COUNTER.idFromName("global-counter");
    const stub = env.COUNTER.get(id);
    return stub.fetch(request);
  },
};
```

---

## Miniflare - Local Development Simulator

Use Miniflare programmatically to simulate Workers locally for testing and development.

```typescript
import { Miniflare } from "miniflare";

// Create a Miniflare instance with inline script
const mf = new Miniflare({
  script: `
    export default {
      async fetch(request, env) {
        const value = await env.MY_KV.get("key");
        return new Response("Value: " + value);
      }
    }
  `,
  modules: true,
  kvNamespaces: ["MY_KV"],
  kvPersist: "./data/kv",
});

// Send a request to the worker
const response = await mf.dispatchFetch("http://localhost:8787/");
console.log(await response.text());

// Access bindings directly for testing
const kv = await mf.getKVNamespace("MY_KV");
await kv.put("key", "test-value");
const value = await kv.get("key");
console.log(value); // "test-value"

// Access D1 database
const db = await mf.getD1Database("DB");
await db.exec("CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY, name TEXT)");
await db.prepare("INSERT INTO users (name) VALUES (?)").bind("Alice").run();

// Access R2 bucket
const bucket = await mf.getR2Bucket("MY_BUCKET");
await bucket.put("file.txt", "Hello, R2!");
const object = await bucket.get("file.txt");
console.log(await object?.text());

// Cleanup
await mf.dispose();
```

---

## Miniflare - Multi-Worker Configuration

Configure multiple Workers with service bindings for microservices architecture.

```typescript
import { Miniflare } from "miniflare";

const mf = new Miniflare({
  workers: [
    {
      name: "gateway",
      modules: true,
      script: `
        export default {
          async fetch(request, env) {
            // Call the auth service
            const authResponse = await env.AUTH_SERVICE.fetch(request);
            if (!authResponse.ok) return authResponse;

            // Forward to API service
            return env.API_SERVICE.fetch(request);
          }
        }
      `,
      serviceBindings: {
        AUTH_SERVICE: "auth",
        API_SERVICE: "api",
      },
    },
    {
      name: "auth",
      modules: true,
      script: `
        export default {
          async fetch(request, env) {
            const token = request.headers.get("Authorization");
            if (token !== "Bearer secret") {
              return new Response("Unauthorized", { status: 401 });
            }
            return new Response("OK");
          }
        }
      `,
    },
    {
      name: "api",
      modules: true,
      script: `
        export default {
          async fetch(request, env) {
            return Response.json({ message: "Hello from API!" });
          }
        }
      `,
      kvNamespaces: ["DATA"],
    },
  ],
  kvPersist: true,
});

// The first worker (gateway) receives all requests
const response = await mf.dispatchFetch("http://localhost/api/data", {
  headers: { Authorization: "Bearer secret" },
});
console.log(await response.json()); // { message: "Hello from API!" }

await mf.dispose();
```

---

## Miniflare - Durable Objects Testing

Test Durable Objects locally with direct access to object instances.

```typescript
import { Miniflare } from "miniflare";

const mf = new Miniflare({
  modules: true,
  script: `
    export class ChatRoom {
      constructor(state, env) {
        this.state = state;
        this.sessions = [];
      }

      async fetch(request) {
        const url = new URL(request.url);

        if (url.pathname === "/join") {
          const name = url.searchParams.get("name");
          const messages = await this.state.storage.get("messages") || [];
          messages.push({ user: name, action: "joined" });
          await this.state.storage.put("messages", messages);
          return Response.json({ success: true, messageCount: messages.length });
        }

        if (url.pathname === "/messages") {
          const messages = await this.state.storage.get("messages") || [];
          return Response.json(messages);
        }

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

    export default {
      async fetch(request, env) {
        const url = new URL(request.url);
        const roomId = url.searchParams.get("room") || "default";
        const id = env.CHAT_ROOM.idFromName(roomId);
        const room = env.CHAT_ROOM.get(id);
        return room.fetch(request);
      }
    }
  `,
  durableObjects: {
    CHAT_ROOM: "ChatRoom",
  },
  durableObjectsPersist: "./data/do",
});

// Test the Durable Object through the worker
const joinResponse = await mf.dispatchFetch(
  "http://localhost/join?room=test&name=Alice"
);
console.log(await joinResponse.json()); // { success: true, messageCount: 1 }

// Get Durable Object namespace for direct testing
const ns = await mf.getDurableObjectNamespace("CHAT_ROOM");
const id = ns.idFromName("test");
const stub = ns.get(id);
const messages = await stub.fetch("http://localhost/messages");
console.log(await messages.json()); // [{ user: "Alice", action: "joined" }]

await mf.dispose();
```

---

## getPlatformProxy - Framework Integration

Use getPlatformProxy to access Cloudflare bindings in Node.js frameworks like Next.js, Remix, or Astro.

```typescript
// For Next.js, Remix, Astro, or any Node.js framework
import { getPlatformProxy } from "wrangler";

// Get platform proxy with bindings from wrangler.jsonc
const { env, cf, ctx, caches, dispose } = await getPlatformProxy<{
  MY_KV: KVNamespace;
  DB: D1Database;
  MY_BUCKET: R2Bucket;
}>();

// Use KV binding
await env.MY_KV.put("session:123", JSON.stringify({ userId: 1 }));
const session = await env.MY_KV.get("session:123", "json");

// Use D1 binding
const users = await env.DB.prepare("SELECT * FROM users WHERE active = ?")
  .bind(true)
  .all();

// Use R2 binding
await env.MY_BUCKET.put("uploads/file.pdf", fileBuffer);

// Access cf properties (request metadata)
console.log(cf.country, cf.city, cf.timezone);

// Use caches
const cache = caches.default;
await cache.put("https://example.com/data", new Response("cached"));

// Clean up when done (important for tests)
await dispose();

// With custom options
const proxy = await getPlatformProxy({
  configPath: "./wrangler.jsonc",
  environment: "production",
  persist: { path: "./.wrangler/state" },
});
```

---

## Wrangler Programmatic API - startWorker

Start a Worker programmatically for custom tooling and advanced development workflows.

```typescript
import { startWorker } from "wrangler";

const worker = await startWorker({
  name: "my-worker",
  entrypoint: "./src/index.ts",
  compatibilityDate: "2024-01-01",
  compatibilityFlags: ["nodejs_compat"],

  bindings: {
    MY_VAR: { type: "plain_text", value: "hello" },
    MY_SECRET: { type: "secret_text", value: "secret123" },
    MY_KV: { type: "kv_namespace", id: "abc123" },
  },

  dev: {
    server: { hostname: "localhost", port: 8787 },
    persist: "./.wrangler/state",
    liveReload: true,
  },

  build: {
    bundle: true,
    minify: false,
    define: {
      "process.env.NODE_ENV": '"development"',
    },
  },
});

// Wait for worker to be ready
await worker.ready;
console.log(`Worker running at ${await worker.url}`);

// Send requests to the worker
const response = await worker.fetch("http://localhost:8787/api/test");
console.log(await response.json());

// Trigger scheduled event
await worker.scheduled({ cron: "* * * * *" });

// Update configuration without restart
await worker.patchConfig({
  bindings: {
    MY_VAR: { type: "plain_text", value: "updated" },
  },
});

// Clean up
await worker.dispose();
```

---

## create-cloudflare (C3) - Project Scaffolding

Quickly scaffold new Cloudflare projects with interactive prompts or predefined templates.

```bash
# Interactive project creation
npm create cloudflare@latest

# Create with specific template
npm create cloudflare@latest my-app -- --template worker-typescript

# Create a Pages project with React
npm create cloudflare@latest my-react-app -- --framework react

# Create with Next.js
npm create cloudflare@latest my-nextjs-app -- --framework next

# Create with Astro
npm create cloudflare@latest my-astro-app -- --framework astro

# Create with SvelteKit
npm create cloudflare@latest my-svelte-app -- --framework svelte

# Create a Hono API project
npm create cloudflare@latest my-api -- --template hono

# Create without deploying
npm create cloudflare@latest my-app -- --no-deploy

# Create in specific directory
npm create cloudflare@latest ./projects/my-worker
```

---

## Cloudflare Vite Plugin

Integrate Vite with Workers for modern frontend development with full runtime API access.

```typescript
// vite.config.ts
import { defineConfig } from "vite";
import { cloudflare } from "@cloudflare/vite-plugin";

export default defineConfig({
  plugins: [cloudflare()],
});

// With React Router v7 or TanStack Start
import { defineConfig } from "vite";
import { cloudflare } from "@cloudflare/vite-plugin";
import { reactRouter } from "@react-router/dev/vite";

export default defineConfig({
  plugins: [
    cloudflare(),
    reactRouter(),
  ],
});

// Custom worker configuration
import { defineConfig } from "vite";
import { cloudflare } from "@cloudflare/vite-plugin";

export default defineConfig({
  plugins: [
    cloudflare({
      configPath: "./wrangler.jsonc",
      // Enable persistent storage during development
      persist: { path: "./.wrangler/state" },
    }),
  ],
});
```

---

## Vitest Pool Workers - Testing

Write and run tests that execute inside the Workers runtime with full binding access.

```typescript
// vitest.config.ts
import { cloudflareTest } from "@cloudflare/vitest-pool-workers";
import { defineConfig } from "vitest/config";

export default defineConfig({
  plugins: [
    cloudflareTest({
      wrangler: { configPath: "./wrangler.jsonc" },
      miniflare: {
        compatibilityFlags: ["service_binding_extra_handlers"],
      },
    }),
  ],
});

// tests/worker.test.ts
import { exports, env } from "cloudflare:workers";
import { describe, it, expect, beforeAll } from "vitest";

describe("Worker", () => {
  beforeAll(async () => {
    // Setup test data
    await env.MY_KV.put("test-key", "test-value");
  });

  it("handles fetch requests", async () => {
    const response = await exports.default.fetch("http://localhost/api/data");
    expect(response.status).toBe(200);

    const data = await response.json();
    expect(data).toHaveProperty("message");
  });

  it("reads from KV", async () => {
    const value = await env.MY_KV.get("test-key");
    expect(value).toBe("test-value");
  });

  it("writes to D1", async () => {
    await env.DB.exec("CREATE TABLE IF NOT EXISTS test (id INTEGER PRIMARY KEY, value TEXT)");
    await env.DB.prepare("INSERT INTO test (value) VALUES (?)").bind("hello").run();

    const result = await env.DB.prepare("SELECT * FROM test").all();
    expect(result.results).toHaveLength(1);
    expect(result.results[0].value).toBe("hello");
  });

  it("triggers scheduled event", async () => {
    const result = await exports.default.scheduled({
      scheduledTime: Date.now(),
      cron: "* * * * *",
    });
    // Verify scheduled handler executed
  });
});

// tests/durable-object.test.ts
import { env } from "cloudflare:workers";
import { describe, it, expect } from "vitest";

describe("Durable Object", () => {
  it("maintains state across requests", async () => {
    const id = env.COUNTER.idFromName("test");
    const stub = env.COUNTER.get(id);

    // First request
    const res1 = await stub.fetch("http://localhost/increment");
    expect(await res1.json()).toEqual({ value: 1 });

    // Second request to same object
    const res2 = await stub.fetch("http://localhost/increment");
    expect(await res2.json()).toEqual({ value: 2 });
  });
});
```

---

## KV Asset Handler

Serve static assets from Workers KV with caching and content-type handling.

```typescript
import {
  getAssetFromKV,
  serveSinglePageApp,
  NotFoundError,
  MethodNotAllowedError,
} from "@cloudflare/kv-asset-handler";
import manifestJSON from "__STATIC_CONTENT_MANIFEST";

const assetManifest = JSON.parse(manifestJSON);

export default {
  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    // API routes
    const url = new URL(request.url);
    if (url.pathname.startsWith("/api/")) {
      return handleApiRequest(request, env);
    }

    // Static assets from KV
    try {
      return await getAssetFromKV(
        { request, waitUntil: (p) => ctx.waitUntil(p) },
        {
          ASSET_NAMESPACE: env.__STATIC_CONTENT,
          ASSET_MANIFEST: assetManifest,
          // Cache settings
          cacheControl: {
            browserTTL: 60 * 60 * 24, // 1 day
            edgeTTL: 60 * 60 * 24 * 7, // 1 week
            bypassCache: false,
          },
          // For SPAs, serve index.html for all routes
          mapRequestToAsset: serveSinglePageApp,
        }
      );
    } catch (e) {
      if (e instanceof NotFoundError) {
        return new Response("Page not found", { status: 404 });
      }
      if (e instanceof MethodNotAllowedError) {
        return new Response("Method not allowed", { status: 405 });
      }
      throw e;
    }
  },
};

// Custom asset mapping example
async function handleWithCustomMapping(request: Request, env: Env, ctx: ExecutionContext) {
  const customKeyModifier = (req: Request) => {
    const url = new URL(req.url);
    // Strip /docs prefix and serve from different path
    const newPath = url.pathname.replace("/docs", "/documentation");
    return new Request(new URL(newPath, url.origin), req);
  };

  return getAssetFromKV(
    { request, waitUntil: (p) => ctx.waitUntil(p) },
    {
      ASSET_NAMESPACE: env.__STATIC_CONTENT,
      ASSET_MANIFEST: assetManifest,
      mapRequestToAsset: customKeyModifier,
    }
  );
}
```

---

## Queues - Message Processing

Process messages asynchronously with Cloudflare Queues for background job handling.

```typescript
// wrangler.jsonc
{
  "queues": {
    "producers": [
      { "binding": "MY_QUEUE", "queue": "my-queue" }
    ],
    "consumers": [
      { "queue": "my-queue", "max_batch_size": 10, "max_retries": 3 }
    ]
  }
}

// src/index.ts
export interface Env {
  MY_QUEUE: Queue<QueueMessage>;
}

interface QueueMessage {
  type: "email" | "notification" | "report";
  payload: Record<string, unknown>;
}

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

    if (url.pathname === "/send-email" && request.method === "POST") {
      const body = await request.json();

      // Send single message
      await env.MY_QUEUE.send({
        type: "email",
        payload: { to: body.email, subject: body.subject },
      });

      return Response.json({ queued: true });
    }

    if (url.pathname === "/bulk-notify" && request.method === "POST") {
      const { userIds } = await request.json();

      // Send batch of messages
      await env.MY_QUEUE.sendBatch(
        userIds.map((id: string) => ({
          body: { type: "notification" as const, payload: { userId: id } },
        }))
      );

      return Response.json({ queued: userIds.length });
    }

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

  // Queue consumer - process messages
  async queue(batch: MessageBatch<QueueMessage>, env: Env): Promise<void> {
    for (const message of batch.messages) {
      try {
        switch (message.body.type) {
          case "email":
            await sendEmail(message.body.payload);
            message.ack();
            break;
          case "notification":
            await sendNotification(message.body.payload);
            message.ack();
            break;
          default:
            // Unknown message type, retry later
            message.retry();
        }
      } catch (error) {
        console.error("Failed to process message:", error);
        message.retry({ delaySeconds: 60 });
      }
    }
  },
};
```

---

## Hyperdrive - Database Connection Pooling

Connect to external PostgreSQL databases with automatic connection pooling.

```typescript
// wrangler.jsonc
{
  "hyperdrive": [
    {
      "binding": "HYPERDRIVE",
      "id": "abc123...",
      "localConnectionString": "postgres://user:pass@localhost:5432/mydb"
    }
  ]
}

// src/index.ts
import { Client } from "pg";

export interface Env {
  HYPERDRIVE: Hyperdrive;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // Get connection string from Hyperdrive (pooled connection)
    const client = new Client({ connectionString: env.HYPERDRIVE.connectionString });

    try {
      await client.connect();

      const url = new URL(request.url);

      if (url.pathname === "/users") {
        const result = await client.query("SELECT id, name, email FROM users LIMIT 100");
        return Response.json(result.rows);
      }

      if (url.pathname === "/user" && request.method === "POST") {
        const { name, email } = await request.json();
        const result = await client.query(
          "INSERT INTO users (name, email) VALUES ($1, $2) RETURNING id",
          [name, email]
        );
        return Response.json({ id: result.rows[0].id });
      }

      return new Response("Not Found", { status: 404 });
    } finally {
      await client.end();
    }
  },
};
```

---

## AI Bindings - Workers AI

Use Cloudflare's AI models for inference directly in your Worker.

```typescript
// wrangler.jsonc
{
  "ai": { "binding": "AI" }
}

// src/index.ts
export interface Env {
  AI: Ai;
}

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

    // Text generation
    if (url.pathname === "/generate") {
      const { prompt } = await request.json();
      const response = await env.AI.run("@cf/meta/llama-2-7b-chat-int8", {
        prompt,
        max_tokens: 256,
      });
      return Response.json(response);
    }

    // Text classification
    if (url.pathname === "/classify") {
      const { text } = await request.json();
      const response = await env.AI.run("@cf/huggingface/distilbert-sst-2-int8", {
        text,
      });
      return Response.json(response);
    }

    // Image classification
    if (url.pathname === "/classify-image") {
      const imageData = await request.arrayBuffer();
      const response = await env.AI.run("@cf/microsoft/resnet-50", {
        image: [...new Uint8Array(imageData)],
      });
      return Response.json(response);
    }

    // Text embeddings
    if (url.pathname === "/embed") {
      const { text } = await request.json();
      const response = await env.AI.run("@cf/baai/bge-base-en-v1.5", {
        text: [text],
      });
      return Response.json(response);
    }

    // Translation
    if (url.pathname === "/translate") {
      const { text, source_lang, target_lang } = await request.json();
      const response = await env.AI.run("@cf/meta/m2m100-1.2b", {
        text,
        source_lang,
        target_lang,
      });
      return Response.json(response);
    }

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

---

## Summary

The Cloudflare Workers SDK provides a complete ecosystem for building serverless applications at the edge. The primary use cases include building API backends with Workers, serving static sites and SPAs with Workers Sites or Assets, processing background jobs with Queues, maintaining stateful applications with Durable Objects, and integrating AI capabilities directly into applications. The SDK excels in scenarios requiring low-latency global distribution, real-time data processing, and seamless integration with Cloudflare's broader platform services.

Integration patterns typically involve using Wrangler CLI for development and deployment workflows, Miniflare for local testing and CI/CD pipelines, the Vite plugin for modern frontend frameworks like React Router and TanStack Start, and the Vitest pool for comprehensive testing. For existing Node.js frameworks like Next.js, Remix, or Astro, the `getPlatformProxy` API provides seamless access to Cloudflare bindings during local development. The monorepo structure ensures all tools work together cohesively, with shared types and utilities enabling type-safe development across the entire stack.