Cloudflare Workers Research

Research Focus: Architecture and patterns for migrating MonoTask's task automation and agent orchestration system to Cloudflare Workers platform.

Workers Architecture Overview
Durable Objects for Queue Management
WebSocket Handling for Real-time Updates
KV Storage for Session Management
Worker-to-Worker Communication
Environment Variables and Secrets
Scheduling and Cron Triggers
Cloudflare Queues
Workflows for Durable Execution
Error Handling and Logging
Performance Limits and Quotas
Cold Start Mitigation Strategies
Code Examples and Patterns

Workers Architecture Overview

V8 Isolate Model

Cloudflare Workers run on V8 isolates rather than containers, providing:

Faster startup: Cold starts in milliseconds vs seconds for containers
Lower overhead: Multiple Workers share a single V8 process
Better density: Higher concurrent execution per machine
Memory isolation: Secure execution boundaries without container overhead

Runtime Environment

Workers support multiple languages and frameworks:

Languages: JavaScript, TypeScript, Python, Rust, WebAssembly
Frameworks: React, Vue, Next.js, Astro, Hono, React Router
APIs: Standard Web APIs (fetch, Request, Response, WebSocket)
No Node.js APIs: Cannot use XMLHttpRequest, filesystem APIs, or Node-specific modules

Request/Response Lifecycle

typescript

export interface Env {
  // Bindings: KV, D1, R2, Durable Objects, etc.
  MY_KV: KVNamespace;
  MY_DURABLE_OBJECT: DurableObjectNamespace;
}

export default {
  async fetch(
    request: Request,
    env: Env,
    ctx: ExecutionContext
  ): Promise<Response> {
    // Process request
    const url = new URL(request.url);
    
    // Access bindings via env
    await env.MY_KV.put("key", "value");
    
    // Extend execution beyond response with ctx.waitUntil()
    ctx.waitUntil(logAnalytics(request));
    
    return new Response("Hello World");
  }
};

Key Parameters:

request: Standard Request object (method, headers, body, URL)
env: Bindings to resources (KV, databases, Durable Objects, secrets)
ctx: Execution context with waitUntil() and passThroughOnException()

Handler Types

Workers support multiple event handler types:

Fetch Handler: HTTP request/response (most common)
Scheduled Handler: Cron-triggered execution
Queue Handler: Process messages from Cloudflare Queues
Tail Handler: Receive logs and diagnostics
Email Handler: Process incoming emails
Alarm Handler: Durable Object scheduled callbacks

Durable Objects for Queue Management

Architecture and Consistency Guarantees

Durable Objects provide:

Global uniqueness: Each object has a unique ID accessible worldwide
Co-located storage: Persistent SQLite storage lives with the compute
Strong consistency: Transactional, serializable storage with no race conditions
Single-threaded execution: One request at a time per object instance
Geographic distribution: Objects provision near request origins

Key characteristics:

Each Durable Object has exactly one active instance globally at any time
All requests to a specific object ID route to the same instance
Perfect for coordination, queues, WebSocket session management

Defining a Durable Object

typescript

import { DurableObject } from "cloudflare:workers";

export class TaskQueue extends DurableObject {
  constructor(ctx: DurableObjectState, env: Env) {
    super(ctx, env);
  }

  async fetch(request: Request): Promise<Response> {
    // Handle incoming requests
    const url = new URL(request.url);
    
    if (url.pathname === "/enqueue") {
      return await this.enqueueTask(request);
    }
    
    return new Response("Not Found", { status: 404 });
  }

  async enqueueTask(request: Request): Promise<Response> {
    const task = await request.json();
    
    // Store in persistent storage
    const queue = await this.ctx.storage.get<Task[]>("queue") || [];
    queue.push({ ...task, id: crypto.randomUUID() });
    await this.ctx.storage.put("queue", queue);
    
    // Set alarm to process queue
    const alarmTime = Date.now() + 1000; // 1 second
    await this.ctx.storage.setAlarm(alarmTime);
    
    return Response.json({ success: true });
  }

  async alarm() {
    // Process queued tasks
    const queue = await this.ctx.storage.get<Task[]>("queue") || [];
    
    if (queue.length > 0) {
      const task = queue.shift();
      await this.processTask(task);
      await this.ctx.storage.put("queue", queue);
      
      // Schedule next alarm if more tasks
      if (queue.length > 0) {
        await this.ctx.storage.setAlarm(Date.now() + 1000);
      }
    }
  }
}

Storage API

The Durable Object Storage API provides strongly consistent, transactional storage:

typescript

interface DurableObjectStorage {
  // Basic operations
  get<T>(key: string): Promise<T | undefined>;
  get<T>(keys: string[]): Promise<Map<string, T>>;
  
  put<T>(key: string, value: T): Promise<void>;
  put(entries: Record<string, any>): Promise<void>;
  
  delete(key: string): Promise<boolean>;
  delete(keys: string[]): Promise<number>;
  
  list<T>(options?: {
    start?: string;
    end?: string;
    prefix?: string;
    reverse?: boolean;
    limit?: number;
  }): Promise<Map<string, T>>;
  
  deleteAll(): Promise<void>;
  
  // Transactions
  transaction<T>(closure: (txn: DurableObjectTransaction) => Promise<T>): Promise<T>;
  
  // SQL (SQLite-backed storage)
  sql: DurableObjectSql;
  
  // Alarms
  getAlarm(): Promise<number | null>;
  setAlarm(scheduledTime: number): Promise<void>;
  deleteAlarm(): Promise<void>;
}

Key features:

Automatic caching: Storage API includes built-in in-memory caching
Atomic operations: Transactions ensure consistency
SQLite backend: Full SQL support for complex queries
10 GB per object: Ample storage for queue state

In-Memory State vs Persistent Storage

In-Memory State:

typescript

export class Counter extends DurableObject {
  private count: number = 0; // In-memory, lost on eviction
  
  constructor(ctx: DurableObjectState, env: Env) {
    super(ctx, env);
    
    // Load from storage once during initialization
    ctx.blockConcurrencyWhile(async () => {
      const stored = await this.ctx.storage.get<number>("count");
      this.count = stored || 0;
    });
  }
  
  async increment(): Promise<number> {
    this.count++;
    // Persist to storage
    await this.ctx.storage.put("count", this.count);
    return this.count;
  }
}

When to use in-memory state:

Frequently accessed values (avoid repeated storage reads)
Temporary session data
Performance-critical hot paths

When to use persistent storage:

Critical data that must survive eviction
Infrequently accessed data
Large datasets

Best practices:

Use blockConcurrencyWhile() in constructor to load initial state
Store state in instance variables (this.value), not globals
Storage API has built-in caching, so repeated get() calls are fast
Combine both: cache frequently accessed values in-memory

Alarms API for Scheduling

typescript

export class ScheduledProcessor extends DurableObject {
  async fetch(request: Request): Promise<Response> {
    // Check for existing alarm
    const currentAlarm = await this.ctx.storage.getAlarm();
    
    if (currentAlarm === null) {
      // Schedule alarm for 10 seconds from now
      await this.ctx.storage.setAlarm(Date.now() + 10000);
    }
    
    return Response.json({ 
      alarmScheduled: currentAlarm !== null,
      nextAlarm: currentAlarm 
    });
  }
  
  async alarm(alarmInfo?: { retryCount: number; isRetry: boolean }) {
    if (alarmInfo?.isRetry) {
      console.log(`Retry attempt ${alarmInfo.retryCount}`);
    }
    
    // Process scheduled work
    await this.processBatchedTasks();
    
    // Optionally schedule next alarm
    await this.ctx.storage.setAlarm(Date.now() + 60000); // 1 minute
  }
  
  async processBatchedTasks() {
    const tasks = await this.ctx.storage.get<Task[]>("pending") || [];
    
    for (const task of tasks) {
      await this.executeTask(task);
    }
    
    await this.ctx.storage.delete("pending");
  }
}

Alarm characteristics:

At-least-once execution: Guaranteed delivery with automatic retries
One alarm per object: Only a single scheduled alarm at a time
Exponential backoff: 2-second initial delay, up to 6 retries
Non-blocking: Only one alarm() executes at a time

Use cases:

Batch processing to reduce costs
Delayed job execution
Distributed queue implementation
Work coordination without incoming requests

Concurrency Control

typescript

export class CriticalSection extends DurableObject {
  constructor(ctx: DurableObjectState, env: Env) {
    super(ctx, env);
    
    // Block all requests during initialization (max 30 seconds)
    ctx.blockConcurrencyWhile(async () => {
      await this.loadComplexState();
    });
  }
  
  async loadComplexState() {
    // Complex initialization that must complete before handling requests
    const data = await this.ctx.storage.get("state");
    // Process data...
  }
}

blockConcurrencyWhile(callback):

Executes async callback while blocking other events
30-second timeout enforced
Commonly used during constructor initialization
Ensures state consistency before request handling

Accessing Durable Objects from Workers

typescript

export interface Env {
  TASK_QUEUE: DurableObjectNamespace<TaskQueue>;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // Get Durable Object by name (deterministic ID)
    const id = env.TASK_QUEUE.idFromName("main-queue");
    
    // Or generate new unique ID
    // const id = env.TASK_QUEUE.newUniqueId();
    
    // Or use existing ID
    // const id = env.TASK_QUEUE.idFromString(idString);
    
    // Get stub (reference to Durable Object)
    const stub = env.TASK_QUEUE.get(id);
    
    // Call methods via RPC
    const result = await stub.enqueueTask({ name: "process" });
    
    // Or forward entire request
    return await stub.fetch(request);
  }
};

ID generation strategies:

idFromName(name): Deterministic ID from string (same name = same object)
newUniqueId(): Random unique ID for new objects
idFromString(hexId): Reconstruct from serialized ID
idFromId(id): Clone existing ID

Location hints:

typescript

const id = env.TASK_QUEUE.idFromName("queue", { 
  locationHint: "enam" // Eastern North America
});

Available regions: wnam, enam, sam, weur, eeur, apac, oc, afr, me

Queue Implementation Pattern

typescript

export class DistributedQueue extends DurableObject {
  private processing: boolean = false;
  
  async enqueue(task: Task): Promise<void> {
    const queue = await this.ctx.storage.get<Task[]>("queue") || [];
    queue.push(task);
    await this.ctx.storage.put("queue", queue);
    
    // Trigger processing if not already running
    if (!this.processing) {
      await this.ctx.storage.setAlarm(Date.now());
    }
  }
  
  async dequeue(): Promise<Task | null> {
    const queue = await this.ctx.storage.get<Task[]>("queue") || [];
    
    if (queue.length === 0) return null;
    
    const task = queue.shift();
    await this.ctx.storage.put("queue", queue);
    
    return task;
  }
  
  async alarm() {
    this.processing = true;
    
    try {
      let task: Task | null;
      
      while ((task = await this.dequeue()) !== null) {
        await this.processTask(task);
      }
    } finally {
      this.processing = false;
    }
  }
  
  async processTask(task: Task): Promise<void> {
    // Execute task logic
    console.log("Processing task:", task.id);
  }
}

WebSocket Handling for Real-time Updates

WebSocketPair API

typescript

export default {
  async fetch(request: Request): Promise<Response> {
    const upgradeHeader = request.headers.get("Upgrade");
    
    if (upgradeHeader !== "websocket") {
      return new Response("Expected WebSocket", { status: 426 });
    }
    
    // Create WebSocket pair (two connected endpoints)
    const pair = new WebSocketPair();
    const [client, server] = [pair[0], pair[1]];
    
    // Accept the WebSocket on Cloudflare's network
    server.accept();
    
    // Handle messages
    server.addEventListener("message", (event) => {
      console.log("Received:", event.data);
      server.send(`Echo: ${event.data}`);
    });
    
    server.addEventListener("close", (event) => {
      console.log("WebSocket closed:", event.code, event.reason);
    });
    
    server.addEventListener("error", (event) => {
      console.error("WebSocket error:", event);
    });
    
    // Return client side to browser
    return new Response(null, {
      status: 101,
      webSocket: client,
    });
  }
};

Key methods:

accept(): Start handling WebSocket on Cloudflare's network
send(message): Send string or binary data (max 1 MiB)
close(code, reason): Terminate connection
addEventListener(type, callback): Listen for message, close, error

Integration with Durable Objects

typescript

export class WebSocketRoom extends DurableObject {
  private sessions: Map<string, WebSocket> = new Map();
  
  async fetch(request: Request): Promise<Response> {
    const upgradeHeader = request.headers.get("Upgrade");
    
    if (upgradeHeader !== "websocket") {
      return new Response("Expected WebSocket", { status: 426 });
    }
    
    const pair = new WebSocketPair();
    const [client, server] = [pair[0], pair[1]];
    
    // Generate unique session ID
    const sessionId = crypto.randomUUID();
    
    // Accept and store connection
    server.accept();
    this.sessions.set(sessionId, server);
    
    // Handle messages
    server.addEventListener("message", (event) => {
      this.broadcast(event.data, sessionId);
    });
    
    server.addEventListener("close", () => {
      this.sessions.delete(sessionId);
      this.broadcast(`User left (${this.sessions.size} online)`, sessionId);
    });
    
    // Send welcome message
    server.send(JSON.stringify({
      type: "welcome",
      sessionId,
      userCount: this.sessions.size
    }));
    
    // Notify others
    this.broadcast(`User joined (${this.sessions.size} online)`, sessionId);
    
    return new Response(null, {
      status: 101,
      webSocket: client,
    });
  }
  
  broadcast(message: string, excludeSession?: string) {
    const payload = JSON.stringify({
      type: "message",
      data: message,
      timestamp: Date.now()
    });
    
    for (const [sessionId, socket] of this.sessions) {
      if (sessionId !== excludeSession) {
        try {
          socket.send(payload);
        } catch (err) {
          // Remove failed connections
          this.sessions.delete(sessionId);
        }
      }
    }
  }
}

// Worker that routes to Durable Object
export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const roomId = env.WEBSOCKET_ROOM.idFromName("main-room");
    const room = env.WEBSOCKET_ROOM.get(roomId);
    return room.fetch(request);
  }
};

WebSocket Hibernation API

Problem: Active WebSocket connections keep Durable Objects in memory, incurring duration charges even when idle.

Solution: WebSocket Hibernation API allows connections to persist while the Durable Object is evicted from memory.

typescript

export class HibernatableRoom extends DurableObject {
  async fetch(request: Request): Promise<Response> {
    const pair = new WebSocketPair();
    const [client, server] = [pair[0], pair[1]];
    
    // Accept WebSocket with Hibernation API
    this.ctx.acceptWebSocket(server, ["chat-room"]);
    
    return new Response(null, {
      status: 101,
      webSocket: client,
    });
  }
  
  // Called when WebSocket message arrives (wakes from hibernation)
  async webSocketMessage(ws: WebSocket, message: string | ArrayBuffer) {
    const data = typeof message === "string" ? message : new TextDecoder().decode(message);
    
    // Broadcast to all WebSockets with tag
    const sockets = this.ctx.getWebSockets("chat-room");
    
    for (const socket of sockets) {
      socket.send(data);
    }
  }
  
  // Called when WebSocket closes
  async webSocketClose(ws: WebSocket, code: number, reason: string, wasClean: boolean) {
    console.log("WebSocket closed:", code, reason);
  }
  
  // Called on WebSocket error
  async webSocketError(ws: WebSocket, error: any) {
    console.error("WebSocket error:", error);
  }
}

Hibernation API methods:

ctx.acceptWebSocket(ws, tags?): Register WebSocket for hibernation
ctx.getWebSockets(tag?): Retrieve active WebSockets by tag
ctx.setWebSocketAutoResponse(pair): Auto-respond to pings (prevent wake-ups)
ctx.getTags(ws): Get tags for a WebSocket
ctx.setHibernatableWebSocketEventTimeout(ms): Set max event runtime (0-604,800,000 ms)

Benefits:

Reduced duration charges for idle connections
Scales to millions of connections
Automatic wake-up on message receipt
Tag-based connection grouping

Broadcasting Patterns

Echo to sender:

typescript

server.addEventListener("message", (event) => {
  server.send(event.data);
});

Broadcast to all except sender:

typescript

broadcast(message: string, excludeSession: string) {
  for (const [sessionId, socket] of this.sessions) {
    if (sessionId !== excludeSession) {
      socket.send(message);
    }
  }
}

Broadcast to all including sender:

typescript

broadcast(message: string) {
  for (const socket of this.sessions.values()) {
    socket.send(message);
  }
}

Tag-based broadcasting (Hibernation API):

typescript

// Send to specific tag
const adminSockets = this.ctx.getWebSockets("admin");
for (const socket of adminSockets) {
  socket.send("Admin message");
}

KV Storage for Session Management

API Overview

Workers KV is a global, eventually consistent, key-value store optimized for high-read workloads with low latency.

Consistency model:

Eventually consistent: Writes propagate globally within seconds
Read-heavy optimized: Excellent for caching, sessions, configuration
Not suitable for: Strong consistency requirements, write-heavy workloads

KV API Methods

typescript

interface KVNamespace {
  // Read operations
  get(key: string, options?: KVGetOptions): Promise<string | null>;
  get(key: string, type: "text"): Promise<string | null>;
  get(key: string, type: "json"): Promise<any>;
  get(key: string, type: "arrayBuffer"): Promise<ArrayBuffer | null>;
  get(key: string, type: "stream"): Promise<ReadableStream | null>;
  
  // Write operations
  put(
    key: string,
    value: string | ArrayBuffer | ReadableStream,
    options?: KVPutOptions
  ): Promise<void>;
  
  // Delete operations
  delete(key: string): Promise<void>;
  
  // List operations
  list(options?: KVListOptions): Promise<KVListResult>;
  
  // Metadata
  getWithMetadata<Metadata>(
    key: string,
    options?: KVGetOptions
  ): Promise<{ value: string | null; metadata: Metadata | null }>;
}

interface KVPutOptions {
  expiration?: number;        // Unix timestamp (seconds)
  expirationTtl?: number;     // Seconds from now
  metadata?: any;             // Custom metadata (max 1024 bytes)
}

interface KVListOptions {
  prefix?: string;
  limit?: number;
  cursor?: string;
}

Session Management Pattern

typescript

export interface Env {
  SESSIONS: KVNamespace;
}

interface SessionData {
  userId: string;
  email: string;
  createdAt: number;
  lastActivity: number;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const url = new URL(request.url);
    
    // Get session ID from cookie
    const sessionId = getSessionCookie(request);
    
    if (!sessionId) {
      return new Response("Unauthorized", { status: 401 });
    }
    
    // Retrieve session from KV
    const session = await env.SESSIONS.get<SessionData>(
      `session:${sessionId}`,
      "json"
    );
    
    if (!session) {
      return new Response("Session expired", { status: 401 });
    }
    
    // Update last activity and extend TTL
    session.lastActivity = Date.now();
    await env.SESSIONS.put(
      `session:${sessionId}`,
      JSON.stringify(session),
      { expirationTtl: 3600 } // 1 hour
    );
    
    return Response.json({ user: session.userId });
  }
};

function getSessionCookie(request: Request): string | null {
  const cookie = request.headers.get("Cookie");
  if (!cookie) return null;
  
  const match = cookie.match(/session=([^;]+)/);
  return match ? match[1] : null;
}

Caching Pattern

typescript

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const url = new URL(request.url);
    const cacheKey = `cache:${url.pathname}`;
    
    // Try cache first
    const cached = await env.CACHE_KV.get(cacheKey, "json");
    
    if (cached) {
      return Response.json(cached, {
        headers: { "X-Cache": "HIT" }
      });
    }
    
    // Cache miss - fetch from origin
    const data = await fetchFromAPI(url.pathname);
    
    // Store in KV with 5 minute TTL
    await env.CACHE_KV.put(
      cacheKey,
      JSON.stringify(data),
      { expirationTtl: 300 }
    );
    
    return Response.json(data, {
      headers: { "X-Cache": "MISS" }
    });
  }
};

Metadata Pattern

typescript

// Store value with metadata
await env.FILES.put(
  "document.pdf",
  pdfContent,
  {
    metadata: {
      uploadedBy: "user@example.com",
      uploadDate: Date.now(),
      fileSize: pdfContent.byteLength,
      contentType: "application/pdf"
    },
    expirationTtl: 86400 // 24 hours
  }
);

// Retrieve with metadata
const { value, metadata } = await env.FILES.getWithMetadata<FileMetadata>(
  "document.pdf",
  "arrayBuffer"
);

if (value && metadata) {
  console.log(`File uploaded by ${metadata.uploadedBy}`);
}

List Keys Pattern

typescript

// List all keys with prefix
async function listUserSessions(env: Env, userId: string): Promise<string[]> {
  const sessions: string[] = [];
  let cursor: string | undefined;
  
  do {
    const result = await env.SESSIONS.list({
      prefix: `session:${userId}:`,
      limit: 1000,
      cursor
    });
    
    sessions.push(...result.keys.map(k => k.name));
    cursor = result.list_complete ? undefined : result.cursor;
  } while (cursor);
  
  return sessions;
}

TTL and Expiration

typescript

// Expire at specific timestamp
await env.KV.put("key", "value", {
  expiration: Math.floor(Date.now() / 1000) + 3600 // 1 hour from now
});

// Expire after duration
await env.KV.put("key", "value", {
  expirationTtl: 3600 // 1 hour
});

Best Practices

Use for read-heavy workloads: KV is optimized for high read volume
Namespace with prefixes: Organize keys with prefixes (session:, cache:, config:)
Set appropriate TTLs: Automatic expiration reduces manual cleanup
Leverage metadata: Store small amounts of contextual data
Handle eventual consistency: Don't rely on immediate read-after-write consistency
Batch operations: Use list() with pagination for bulk operations
Keep values small: Optimize for quick retrieval (<25 KB ideal)

Worker-to-Worker Communication

Service Bindings Overview

Service bindings enable Workers to call other Workers directly without HTTP round-trips or public URLs.

Benefits:

Zero latency overhead: Workers run on the same thread by default
No additional cost: Inter-Worker calls don't count as billable requests
Type safety: Full TypeScript support with RPC
Smart Placement: Optional geographic optimization

RPC vs HTTP Communication

RPC (Recommended):

Type-safe method calls
Direct function invocation
Complex object passing
IDE autocomplete support

HTTP:

Traditional REST patterns
Standard request/response
Framework compatibility
External service compatibility

RPC Implementation

Service Worker (provides functionality):

typescript

import { WorkerEntrypoint } from "cloudflare:workers";

export interface Env {
  DATABASE: D1Database;
}

// Export RPC methods via WorkerEntrypoint
export class TaskService extends WorkerEntrypoint<Env> {
  async getTask(taskId: string): Promise<Task | null> {
    const result = await this.env.DATABASE
      .prepare("SELECT * FROM tasks WHERE id = ?")
      .bind(taskId)
      .first<Task>();
    
    return result;
  }
  
  async createTask(data: CreateTaskData): Promise<Task> {
    const id = crypto.randomUUID();
    
    await this.env.DATABASE
      .prepare("INSERT INTO tasks (id, title, status) VALUES (?, ?, ?)")
      .bind(id, data.title, "pending")
      .run();
    
    return { id, ...data, status: "pending" };
  }
  
  async updateTaskStatus(taskId: string, status: TaskStatus): Promise<void> {
    await this.env.DATABASE
      .prepare("UPDATE tasks SET status = ? WHERE id = ?")
      .bind(status, taskId)
      .run();
  }
}

export default TaskService;

Consumer Worker (calls service):

typescript

export interface Env {
  TASK_SERVICE: Service<TaskService>; // Type-safe binding
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const url = new URL(request.url);
    
    if (url.pathname === "/tasks") {
      // Direct RPC method call with type safety
      const task = await env.TASK_SERVICE.getTask("task-123");
      
      return Response.json(task);
    }
    
    if (url.pathname === "/tasks/create") {
      const data = await request.json<CreateTaskData>();
      
      // Type-safe method call
      const newTask = await env.TASK_SERVICE.createTask(data);
      
      return Response.json(newTask, { status: 201 });
    }
    
    return new Response("Not Found", { status: 404 });
  }
};

Configuration in wrangler.toml:

toml

# Consumer Worker
name = "api-worker"

[[services]]
binding = "TASK_SERVICE"
service = "task-service-worker"
entrypoint = "TaskService"  # Specify the WorkerEntrypoint class

# Service Worker
# (in separate wrangler.toml for task-service-worker)
name = "task-service-worker"

HTTP Service Binding

typescript

export interface Env {
  AUTH_SERVICE: Fetcher; // HTTP-based service binding
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // Forward request to another Worker
    const authResponse = await env.AUTH_SERVICE.fetch(
      new Request("http://auth/verify", {
        method: "POST",
        headers: { "Authorization": request.headers.get("Authorization") || "" }
      })
    );
    
    if (!authResponse.ok) {
      return new Response("Unauthorized", { status: 401 });
    }
    
    const user = await authResponse.json();
    return Response.json({ user });
  }
};

Context Passing with ctx.props

typescript

// Frontend Worker
export interface Env {
  DOC_WORKER: Service<DocumentWorker>;
}

export default {
  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    // Pass context to service worker
    ctx.props = { 
      requestId: crypto.randomUUID(),
      userId: "user-123" 
    };
    
    return env.DOC_WORKER.fetch(request);
  }
};

// Document Worker
export class DocumentWorker extends WorkerEntrypoint<Env> {
  async fetch(request: Request): Promise<Response> {
    // Access props passed from caller
    const { requestId, userId } = this.ctx.props as { 
      requestId: string; 
      userId: string; 
    };
    
    console.log(`Processing request ${requestId} for user ${userId}`);
    
    return Response.json({ success: true });
  }
}

TypeScript Type Safety

typescript

// types.ts (shared types)
export interface TaskService {
  getTask(id: string): Promise<Task | null>;
  createTask(data: CreateTaskData): Promise<Task>;
  updateTaskStatus(id: string, status: TaskStatus): Promise<void>;
  listTasks(filters: TaskFilters): Promise<Task[]>;
}

export interface Task {
  id: string;
  title: string;
  status: TaskStatus;
  createdAt: number;
}

// service-worker.ts
import { WorkerEntrypoint } from "cloudflare:workers";
import type { TaskService as ITaskService } from "./types";

export class TaskService extends WorkerEntrypoint<Env> implements ITaskService {
  async getTask(id: string): Promise<Task | null> {
    // Implementation with full type checking
  }
  
  // ... other methods
}

// consumer-worker.ts
import type { TaskService } from "./service-worker";

export interface Env {
  TASK_SERVICE: Service<TaskService>;
}

// Now env.TASK_SERVICE has full TypeScript autocomplete!

Performance Characteristics

Same-thread execution: By default, service bindings run on the same isolate
No serialization: Objects passed directly without JSON encoding
No network latency: Direct function calls within the runtime
Smart Placement: Optional geographic optimization for multi-region deployments

Environment Variables and Secrets

Configuration via env Parameter

All configuration is accessed through the env parameter in handler functions:

typescript

export interface Env {
  // Environment variables (plain text)
  ENVIRONMENT: string;
  API_BASE_URL: string;
  
  // Secrets (encrypted)
  ANTHROPIC_API_KEY: string;
  DATABASE_URL: string;
  GITHUB_CLIENT_SECRET: string;
  
  // Bindings
  KV: KVNamespace;
  DB: D1Database;
  QUEUE: Queue;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // Access environment variables
    const apiUrl = env.API_BASE_URL;
    
    // Access secrets (same API, but encrypted at rest)
    const apiKey = env.ANTHROPIC_API_KEY;
    
    // Use in API calls
    const response = await fetch(`${apiUrl}/endpoint`, {
      headers: {
        "Authorization": `Bearer ${apiKey}`
      }
    });
    
    return response;
  }
};

wrangler.toml Configuration

toml

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

# Environment variables (committed to version control)
[vars]
ENVIRONMENT = "production"
API_BASE_URL = "https://api.example.com"
LOG_LEVEL = "info"

# KV Namespace bindings
[[kv_namespaces]]
binding = "KV"
id = "your-kv-namespace-id"

# Durable Object bindings
[[durable_objects.bindings]]
name = "TASK_QUEUE"
class_name = "TaskQueue"

# Service bindings
[[services]]
binding = "AUTH_SERVICE"
service = "auth-worker"

# Queue bindings
[[queues.producers]]
binding = "TASK_QUEUE"
queue = "task-processing-queue"

[[queues.consumers]]
queue = "task-processing-queue"
max_batch_size = 10
max_batch_timeout = 30

Secrets Management

Setting secrets via Wrangler CLI:

bash

# Set a secret (encrypted, not in wrangler.toml)
wrangler secret put ANTHROPIC_API_KEY

# You'll be prompted to enter the value
# The secret is encrypted and stored separately from your code

# List secrets (values not shown)
wrangler secret list

# Delete a secret
wrangler secret delete ANTHROPIC_API_KEY

Accessing secrets in code:

typescript

export interface Env {
  ANTHROPIC_API_KEY: string;
  GITHUB_TOKEN: string;
  ENCRYPTION_KEY: string;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // Secrets accessed identically to environment variables
    const apiKey = env.ANTHROPIC_API_KEY;
    
    // Never log secrets!
    console.log("API key loaded"); // Good
    // console.log(apiKey); // BAD - don't log secrets
    
    return Response.json({ success: true });
  }
};

Per-environment configuration:

toml

# Development environment
[env.development]
vars = { ENVIRONMENT = "development", API_BASE_URL = "http://localhost:3000" }

# Staging environment
[env.staging]
vars = { ENVIRONMENT = "staging", API_BASE_URL = "https://staging.example.com" }

# Production environment
[env.production]
vars = { ENVIRONMENT = "production", API_BASE_URL = "https://api.example.com" }

Deploy to specific environment:

bash

wrangler deploy --env production

Best Practices

Never commit secrets: Use wrangler secret CLI, not wrangler.toml
Type your Env interface: Provides autocomplete and type checking
Use per-environment configs: Separate dev/staging/production settings
Validate required vars: Check for missing configuration on startup
Don't log secrets: Avoid accidentally exposing sensitive data
Rotate secrets regularly: Update API keys and tokens periodically

Scheduling and Cron Triggers

Scheduled Handler Implementation

typescript

export interface Env {
  TASK_QUEUE: Queue;
  KV: KVNamespace;
}

export default {
  // HTTP handler
  async fetch(request: Request, env: Env): Promise<Response> {
    return Response.json({ status: "ok" });
  },
  
  // Scheduled handler (cron trigger)
  async scheduled(
    controller: ScheduledController,
    env: Env,
    ctx: ExecutionContext
  ): Promise<void> {
    // Access cron pattern
    console.log("Cron:", controller.cron);
    
    // Scheduled at timestamp
    console.log("Scheduled at:", controller.scheduledTime);
    
    // Perform maintenance tasks
    ctx.waitUntil(performMaintenance(env));
  }
};

async function performMaintenance(env: Env): Promise<void> {
  // Clean up expired sessions
  await cleanupExpiredSessions(env.KV);
  
  // Queue background tasks
  await env.TASK_QUEUE.send({
    type: "daily-report",
    timestamp: Date.now()
  });
  
  console.log("Maintenance completed");
}

Cron Configuration

toml

name = "scheduled-worker"
main = "src/index.ts"

# Multiple cron triggers supported
[triggers]
crons = [
  "0 */6 * * *",      # Every 6 hours
  "0 0 * * *",        # Daily at midnight UTC
  "0 0 * * 1",        # Weekly on Monday at midnight
  "*/15 * * * *"      # Every 15 minutes
]

Cron syntax:

┌───────────── minute (0 - 59)
│ ┌───────────── hour (0 - 23)
│ │ ┌───────────── day of month (1 - 31)
│ │ │ ┌───────────── month (1 - 12)
│ │ │ │ ┌───────────── day of week (0 - 6) (Sunday to Saturday)
│ │ │ │ │
* * * * *

Common patterns:

0 0 * * * - Daily at midnight UTC
0 */4 * * * - Every 4 hours
*/30 * * * * - Every 30 minutes
0 9 * * 1-5 - Weekdays at 9 AM UTC
0 0 1 * * - First day of each month

Integration with Queues

typescript

export default {
  async scheduled(
    controller: ScheduledController,
    env: Env,
    ctx: ExecutionContext
  ): Promise<void> {
    // Enqueue tasks for asynchronous processing
    const tasks = await generateDailyTasks();
    
    for (const task of tasks) {
      await env.TASK_QUEUE.send(task);
    }
    
    console.log(`Enqueued ${tasks.length} tasks`);
  }
};

Integration with Workflows

typescript

export default {
  async scheduled(
    controller: ScheduledController,
    env: Env,
    ctx: ExecutionContext
  ): Promise<void> {
    // Trigger long-running workflow
    const workflow = await env.WORKFLOW.create({
      id: `daily-${Date.now()}`,
      params: { date: new Date().toISOString() }
    });
    
    console.log("Workflow started:", workflow.id);
  }
};

Local Testing

bash

# Start dev server with scheduled event testing
wrangler dev --test-scheduled

# Trigger scheduled handler manually
curl "http://localhost:8787/__scheduled?cron=0+0+*+*+*"

Use Cases

Data aggregation: Periodic rollups and analytics
Cleanup tasks: Delete expired data, prune logs
Report generation: Daily/weekly automated reports
External API polling: Check for updates from third-party services
Background maintenance: Database optimization, cache warming
Reminder notifications: Scheduled alerts and notifications
Batch processing: Trigger data processing pipelines

Cloudflare Queues

Cloudflare Queues provide guaranteed message delivery with automatic retries, ideal for asynchronous task processing.

Producer API

typescript

export interface Env {
  TASK_QUEUE: Queue;
}

// Send individual message
export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const task = await request.json();
    
    // Send to queue
    await env.TASK_QUEUE.send(task, {
      contentType: "json",  // "text" | "bytes" | "json" | "v8"
      delaySeconds: 10       // Delay delivery (0-43200 seconds)
    });
    
    return Response.json({ queued: true });
  }
};

// Send batch
export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const tasks = await request.json<Task[]>();
    
    // Send up to 100 messages, max 256 KB total
    await env.TASK_QUEUE.sendBatch(
      tasks.map(task => ({
        body: task,
        contentType: "json" as const,
        delaySeconds: 0
      }))
    );
    
    return Response.json({ queued: tasks.length });
  }
};

Consumer API

typescript

export interface Env {
  // No binding needed for consumer
}

export default {
  async queue(
    batch: MessageBatch<Task>,
    env: Env,
    ctx: ExecutionContext
  ): Promise<void> {
    console.log(`Processing batch of ${batch.messages.length} messages`);
    
    for (const message of batch.messages) {
      try {
        await processTask(message.body);
        
        // Explicit acknowledgment (optional, auto-acks on success)
        message.ack();
        
      } catch (error) {
        console.error(`Task ${message.id} failed:`, error);
        
        // Retry with delay
        message.retry({
          delaySeconds: Math.pow(2, message.attempts) // Exponential backoff
        });
      }
    }
  }
};

async function processTask(task: Task): Promise<void> {
  console.log("Processing:", task.id);
  // Task logic here
}

Message Structure

typescript

interface Message<Body = unknown> {
  readonly id: string;           // Unique message ID
  readonly timestamp: Date;      // When message was sent
  readonly body: Body;           // Message payload
  readonly attempts: number;     // Delivery attempt count
  
  ack(): void;                   // Acknowledge successful processing
  retry(options?: {              // Retry with delay
    delaySeconds?: number;
  }): void;
}

interface MessageBatch<Body = unknown> {
  readonly queue: string;        // Queue name
  readonly messages: Message<Body>[];
  
  ackAll(): void;                // Acknowledge all messages
  retryAll(options?: {           // Retry all messages
    delaySeconds?: number;
  }): void;
}

Configuration

toml

name = "queue-producer"

# Producer binding
[[queues.producers]]
binding = "TASK_QUEUE"
queue = "task-processing-queue"

# Consumer configuration
[[queues.consumers]]
queue = "task-processing-queue"
max_batch_size = 10           # Messages per batch (1-100)
max_batch_timeout = 30        # Seconds to wait for batch (0-30)
max_retries = 3               # Retry attempts before DLQ
max_concurrency = 1           # Concurrent batches (1-10)
dead_letter_queue = "failed-tasks"  # Optional DLQ

Retry Pattern with Exponential Backoff

typescript

export default {
  async queue(batch: MessageBatch<Task>, env: Env): Promise<void> {
    for (const message of batch.messages) {
      try {
        await processTaskWithTimeout(message.body, 30000);
        message.ack();
        
      } catch (error) {
        const isRetryable = error instanceof NetworkError;
        
        if (isRetryable && message.attempts < 5) {
          // Exponential backoff: 2s, 4s, 8s, 16s, 32s
          const delaySeconds = Math.min(Math.pow(2, message.attempts), 300);
          
          console.log(`Retrying in ${delaySeconds}s (attempt ${message.attempts + 1})`);
          message.retry({ delaySeconds });
          
        } else {
          // Give up, send to DLQ
          console.error(`Task ${message.id} permanently failed after ${message.attempts} attempts`);
          message.ack(); // Acknowledge to prevent further retries
          
          // Optionally log to monitoring system
          await logFailedTask(env, message);
        }
      }
    }
  }
};

Dead Letter Queue

toml

# Main queue consumer
[[queues.consumers]]
queue = "tasks"
max_retries = 3
dead_letter_queue = "failed-tasks"

# DLQ consumer for failed messages
[[queues.consumers]]
queue = "failed-tasks"
max_batch_size = 1

typescript

// DLQ consumer for manual intervention
export default {
  async queue(batch: MessageBatch<FailedTask>, env: Env): Promise<void> {
    for (const message of batch.messages) {
      // Log to monitoring system
      await logToSentry({
        message: "Task permanently failed",
        task: message.body,
        attempts: message.attempts
      });
      
      // Store for manual review
      await env.FAILED_TASKS_KV.put(
        message.id,
        JSON.stringify({
          task: message.body,
          attempts: message.attempts,
          timestamp: message.timestamp
        })
      );
      
      message.ack();
    }
  }
};

Limits

Message size: 128 KB per message
Batch size: 100 messages or 256 KB total
Delay: 0-43,200 seconds (12 hours)
Retention: Messages retained until processed or max retries exceeded
Throughput: High throughput with automatic scaling

Queues vs Durable Objects

Use Queues when:

Need guaranteed delivery and retries
Processing can be delayed (asynchronous)
Batch processing is efficient
Order doesn't matter (messages processed concurrently)

Use Durable Objects when:

Need strong consistency and coordination
Real-time processing required
Order matters (single-threaded execution)
Complex state management needed

Workflows for Durable Execution

Workflows enable building multi-step, long-running processes with automatic state persistence and retries.

Key Differences from Workers

Feature	Workers	Workflows
Duration	Request-scoped (CPU time limits)	Days or weeks
State	Ephemeral	Automatically persisted
Retries	Manual	Automatic
Use case	HTTP requests, short tasks	Multi-step processes

Workflow Definition

typescript

import { WorkflowEntrypoint, WorkflowStep, WorkflowEvent } from "cloudflare:workers";

export interface Env {
  TASK_WORKFLOW: Workflow;
}

interface TaskWorkflowParams {
  taskId: string;
  userId: string;
}

export class TaskWorkflow extends WorkflowEntrypoint<Env, TaskWorkflowParams> {
  async run(event: WorkflowEvent<TaskWorkflowParams>, step: WorkflowStep) {
    const { taskId, userId } = event.payload;
    
    // Step 1: Elicit requirements
    const requirements = await step.do("elicit-requirements", async () => {
      return await this.elicitRequirements(taskId);
    });
    
    // Step 2: Generate plan
    const plan = await step.do("generate-plan", async () => {
      return await this.generatePlan(taskId, requirements);
    });
    
    // Step 3: Wait for approval (human-in-the-loop)
    const approval = await step.waitForEvent<ApprovalEvent>("approval", {
      timeout: "24 hours"
    });
    
    if (!approval.approved) {
      return { status: "rejected", reason: approval.reason };
    }
    
    // Step 4: Execute implementation
    const implementation = await step.do("implement", async () => {
      return await this.implementTask(taskId, plan);
    });
    
    // Step 5: Run validation
    const validation = await step.do("validate", async () => {
      return await this.validateImplementation(taskId, implementation);
    });
    
    // Step 6: Sleep before final check
    await step.sleep("wait-for-ci", "5 minutes");
    
    // Step 7: Final verification
    const ciResult = await step.do("check-ci", async () => {
      return await this.checkCIStatus(taskId);
    });
    
    return {
      status: ciResult.passed ? "completed" : "failed",
      taskId,
      results: {
        requirements,
        plan,
        implementation,
        validation,
        ci: ciResult
      }
    };
  }
  
  async elicitRequirements(taskId: string): Promise<Requirements> {
    // AI agent interaction
    return { /* ... */ };
  }
  
  // ... other methods
}

Triggering Workflows

typescript

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const { taskId, userId } = await request.json();
    
    // Start workflow
    const instance = await env.TASK_WORKFLOW.create({
      params: { taskId, userId }
    });
    
    return Response.json({
      workflowId: instance.id,
      status: "started"
    });
  }
};

Workflow Events (Human-in-the-Loop)

typescript

// Send event to waiting workflow
export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const { workflowId, approved, reason } = await request.json();
    
    const instance = await env.TASK_WORKFLOW.get(workflowId);
    
    await instance.sendEvent("approval", {
      approved,
      reason
    });
    
    return Response.json({ success: true });
  }
};

State Persistence

Workflows automatically persist state between steps:

No manual checkpointing required
Automatic retries on failures
Resume from last completed step
Survive infrastructure failures

Use Cases for AI Agents

Multi-phase agent execution:
- Elicitation → Planning → Implementation → Validation
- State persisted between phases
- Human review checkpoints with waitForEvent()
Long-running analysis:
- Data collection spanning hours
- Periodic progress updates
- Automatic retries on transient failures
Orchestration:
- Coordinate multiple specialized agents
- Chain agent outputs as inputs
- Parallel agent execution with step.parallel()
Scheduled agent tasks:
- Periodic data processing
- Scheduled report generation
- Time-delayed follow-ups

Error Handling and Logging

Console Logging

typescript

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // Basic logging
    console.log("Request received:", request.url);
    console.info("Processing task");
    console.warn("Rate limit approaching");
    console.error("Failed to process:", error);
    
    // Structured logging
    console.log(JSON.stringify({
      level: "info",
      timestamp: Date.now(),
      requestId: crypto.randomUUID(),
      path: new URL(request.url).pathname,
      method: request.method
    }));
    
    return Response.json({ success: true });
  }
};

Error Handling Patterns

typescript

export default {
  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    try {
      const result = await processRequest(request, env);
      return Response.json(result);
      
    } catch (error) {
      // Log error details
      console.error("Request failed:", {
        error: error instanceof Error ? error.message : String(error),
        stack: error instanceof Error ? error.stack : undefined,
        url: request.url,
        method: request.method
      });
      
      // Return appropriate error response
      if (error instanceof ValidationError) {
        return Response.json(
          { error: error.message },
          { status: 400 }
        );
      }
      
      if (error instanceof AuthenticationError) {
        return Response.json(
          { error: "Unauthorized" },
          { status: 401 }
        );
      }
      
      // Generic error response
      return Response.json(
        { error: "Internal server error" },
        { status: 500 }
      );
    }
  }
};

// Custom error classes
class ValidationError extends Error {
  constructor(message: string) {
    super(message);
    this.name = "ValidationError";
  }
}

class AuthenticationError extends Error {
  constructor(message: string) {
    super(message);
    this.name = "AuthenticationError";
  }
}

ctx.passThroughOnException()

typescript

export default {
  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    // Forward to origin if Worker throws
    ctx.passThroughOnException();
    
    // Your Worker logic
    return processRequest(request, env);
  }
};

ctx.waitUntil() for Background Tasks

typescript

export default {
  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    // Respond immediately
    const response = Response.json({ success: true });
    
    // Continue processing after response sent
    ctx.waitUntil(async () => {
      try {
        await logAnalytics(request, env);
        await updateCache(request, env);
      } catch (error) {
        console.error("Background task failed:", error);
      }
    }());
    
    return response;
  }
};

Workers Logpush

Export logs to external systems:

Cloudflare R2
Amazon S3
Google Cloud Storage
Datadog
Splunk
New Relic

Configuration (via Dashboard or API):

Select destination service
Configure authentication
Filter log fields
Set sampling rate

Tail Workers (Beta)

Process logs from other Workers in real-time:

typescript

export default {
  async tail(events: TraceItem[], env: Env): Promise<void> {
    for (const event of events) {
      // Filter errors
      if (event.outcome === "exception" || event.outcome === "exceededCpu") {
        // Send to monitoring system
        await sendToSentry({
          error: event.exceptions[0],
          scriptName: event.scriptName,
          timestamp: event.eventTimestamp
        });
      }
      
      // Log all console messages
      for (const log of event.logs) {
        console.log(`[${event.scriptName}] ${log.message}`);
      }
    }
  }
};

Monitoring Best Practices

Structured logging: Use JSON for machine-readable logs
Request IDs: Track requests across services
Error context: Include stack traces and relevant data
Sampling: Log subset of requests in high-traffic scenarios
External monitoring: Integrate with Sentry, Datadog, etc.
Metrics: Track success/failure rates, latency, throughput
Alerting: Set up alerts for error rate spikes

Performance Limits and Quotas

Worker Execution Limits

Limit	Free Tier	Paid Tier	Notes
CPU Time	10ms	30ms (default), configurable to 5 minutes	Per request, includes all subrequests
Duration	No limit	No limit	Wall-clock time, but CPU time enforced
Memory	128 MB	128 MB	Per Worker instance
Script Size	1 MB	10 MB	After compression
Environment Variables	64 KB	5 KB per var, 64 KB total	-

Request Limits

Limit	Free Tier	Paid Tier
Daily Requests	100,000	Unlimited (pay-per-use)
Burst Rate	1,000 req/min	Unlimited
Request Size	100 MB	500 MB
Response Size	100 MB	500 MB
Subrequests	50 per request	1,000 per request
Subrequest Duration	30 seconds	30 seconds

Durable Objects Limits

Limit	Value	Notes
Storage per Object	10 GB	SQLite-backed storage
Storage per Account	5 GB (Free), Unlimited (Paid)	-
CPU Time	30s (default), 5 min (configurable)	Resets per HTTP/WebSocket message
Request Throughput	~1,000 req/sec per object	Soft limit
WebSocket Message Size	1 MiB	Received messages
Key/Value Size	2 MB combined	Legacy KV storage
SQL Row Size	2 MB	SQLite backend
SQL Columns	100 per table	-
SQL Statement Length	100 KB	-
Durable Object Classes	100 (Free), 500 (Paid)	-

KV Limits

Limit	Value
Key Size	512 bytes (UTF-8)
Value Size	25 MB
Metadata Size	1,024 bytes
Keys per Namespace	Unlimited
List Operations	1,000 keys per call
Write Rate	1 write/sec per key (eventually consistent)
Read Rate	Unlimited

Queue Limits

Limit	Value
Message Size	128 KB
Batch Size	100 messages or 256 KB
Max Delay	43,200 seconds (12 hours)
Max Batch Timeout	30 seconds
Max Concurrency	10 concurrent batches

Miscellaneous Limits

Limit	Free Tier	Paid Tier
Routes per Zone	1,000	1,000
Custom Domains per Zone	-	100
Simultaneous Connections	-	-
WebSocket Connections	No hard limit	No hard limit

Quota Recommendations

For MonoTask migration:

Paid tier required: AI agent execution likely exceeds 10ms CPU time
Configure CPU time: Set to 5 minutes for long-running agent tasks
Durable Objects: Use for task queue management and state
Queues: Batch task processing to optimize throughput
KV: Session management and caching
Monitor usage: Track CPU time and request counts

Cold Start Mitigation Strategies

Understanding Cold Starts

Workers have near-instant cold starts (milliseconds) due to V8 isolates, but optimization is still important.

Cold start triggers:

First request after deployment
Geographic distribution (new edge location)
Eviction due to inactivity

Optimization Strategies

1. Minimize Module Imports

typescript

// BAD: Large bundle size
import _ from "lodash";
import moment from "moment";

// GOOD: Import only what you need
import { debounce } from "lodash-es";
import { format } from "date-fns";

2. Lazy Loading

typescript

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const url = new URL(request.url);
    
    if (url.pathname === "/complex") {
      // Load module only when needed
      const { processComplex } = await import("./complex-handler");
      return processComplex(request, env);
    }
    
    // Fast path doesn't load heavy modules
    return Response.json({ status: "ok" });
  }
};

3. Reduce Script Size

bash

# Use esbuild or Rollup for tree-shaking
esbuild src/index.ts --bundle --minify --outfile=dist/worker.js

# Wrangler automatically bundles and minifies
wrangler deploy

4. Avoid Heavy Initialization

typescript

// BAD: Heavy computation at module level
const largeConfig = computeExpensiveConfig();

export default {
  async fetch(request: Request): Promise<Response> {
    return Response.json(largeConfig);
  }
};

// GOOD: Lazy initialization
let cachedConfig: Config | null = null;

export default {
  async fetch(request: Request): Promise<Response> {
    if (!cachedConfig) {
      cachedConfig = await loadConfig();
    }
    return Response.json(cachedConfig);
  }
};

5. Use Durable Objects for Warm State

typescript

// Durable Object stays warm across requests
export class WarmCache extends DurableObject {
  private cache: Map<string, any> = new Map();
  
  constructor(ctx: DurableObjectState, env: Env) {
    super(ctx, env);
    
    // Load data once, reuse across requests
    ctx.blockConcurrencyWhile(async () => {
      const stored = await this.ctx.storage.get("cache");
      this.cache = stored || new Map();
    });
  }
  
  async fetch(request: Request): Promise<Response> {
    // In-memory cache persists across requests
    return Response.json(Array.from(this.cache.entries()));
  }
}

6. Smart Placement (Durable Objects)

typescript

// Create Durable Object near users
const id = env.CACHE.idFromName("user-123", {
  locationHint: "enam" // Eastern North America
});

7. Pre-warm Critical Paths

bash

# Deploy with health check endpoint
curl https://your-worker.workers.dev/health

# Pre-warm multiple regions
for region in us-east us-west eu-west; do
  curl https://your-worker.workers.dev/health
done

8. Use Compatibility Dates Wisely

toml

# Stay current to benefit from runtime optimizations
compatibility_date = "2024-01-01"

Cold Start Impact by Architecture

Pattern	Cold Start Impact	Mitigation
Simple API	Minimal (<10ms)	No action needed
Heavy imports	Medium (10-50ms)	Tree-shake, lazy load
Durable Objects	Low (isolate reuse)	Keep objects active
Service Bindings	Minimal (same thread)	No action needed
External APIs	N/A (network bound)	Use KV caching

Monitoring Cold Starts

typescript

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const startTime = Date.now();
    
    // Your logic here
    const result = await processRequest(request, env);
    
    const duration = Date.now() - startTime;
    
    // Log potential cold starts
    if (duration > 100) {
      console.warn("Slow request detected:", {
        duration,
        path: new URL(request.url).pathname,
        possibleColdStart: true
      });
    }
    
    return result;
  }
};

Code Examples and Patterns

Complete API Endpoint Pattern

typescript

import { Hono } from "hono";
import { cors } from "hono/cors";
import { logger } from "hono/logger";

export interface Env {
  DB: D1Database;
  KV: KVNamespace;
  TASK_QUEUE: DurableObjectNamespace<TaskQueue>;
  ANTHROPIC_API_KEY: string;
}

const app = new Hono<{ Bindings: Env }>();

// Middleware
app.use("*", cors());
app.use("*", logger());

// Error handler
app.onError((err, c) => {
  console.error("Request failed:", err);
  return c.json({ error: "Internal server error" }, 500);
});

// Routes
app.get("/", (c) => c.json({ status: "ok" }));

app.get("/tasks", async (c) => {
  const tasks = await c.env.DB
    .prepare("SELECT * FROM tasks ORDER BY created_at DESC LIMIT 100")
    .all();
  
  return c.json(tasks.results);
});

app.post("/tasks", async (c) => {
  const body = await c.req.json<{ title: string; description: string }>();
  
  const id = crypto.randomUUID();
  
  await c.env.DB
    .prepare("INSERT INTO tasks (id, title, description, status) VALUES (?, ?, ?, ?)")
    .bind(id, body.title, body.description, "pending")
    .run();
  
  // Enqueue for processing
  const queueId = c.env.TASK_QUEUE.idFromName("main-queue");
  const queue = c.env.TASK_QUEUE.get(queueId);
  await queue.enqueue({ taskId: id });
  
  return c.json({ id, status: "created" }, 201);
});

app.get("/tasks/:id", async (c) => {
  const id = c.req.param("id");
  
  // Check cache first
  const cached = await c.env.KV.get(`task:${id}`, "json");
  if (cached) {
    return c.json(cached);
  }
  
  // Fetch from database
  const task = await c.env.DB
    .prepare("SELECT * FROM tasks WHERE id = ?")
    .bind(id)
    .first();
  
  if (!task) {
    return c.json({ error: "Not found" }, 404);
  }
  
  // Cache for 5 minutes
  await c.env.KV.put(`task:${id}`, JSON.stringify(task), {
    expirationTtl: 300
  });
  
  return c.json(task);
});

export default app;

Task Queue with Durable Objects (Complete Example)

typescript

import { DurableObject } from "cloudflare:workers";

export interface Env {
  TASK_QUEUE: DurableObjectNamespace<TaskQueue>;
  TASK_PROCESSOR: Queue;
}

interface Task {
  id: string;
  type: string;
  payload: any;
  priority: number;
  createdAt: number;
}

export class TaskQueue extends DurableObject {
  private processing: boolean = false;
  
  async enqueue(task: Task): Promise<void> {
    // Get current queue
    const queue = await this.ctx.storage.get<Task[]>("queue") || [];
    
    // Add task with priority
    queue.push(task);
    queue.sort((a, b) => b.priority - a.priority);
    
    await this.ctx.storage.put("queue", queue);
    
    // Trigger processing
    if (!this.processing) {
      await this.ctx.storage.setAlarm(Date.now());
    }
  }
  
  async dequeue(): Promise<Task | null> {
    const queue = await this.ctx.storage.get<Task[]>("queue") || [];
    
    if (queue.length === 0) return null;
    
    const task = queue.shift();
    await this.ctx.storage.put("queue", queue);
    
    return task;
  }
  
  async alarm() {
    this.processing = true;
    
    try {
      let task: Task | null;
      let processed = 0;
      
      // Process up to 10 tasks per alarm
      while ((task = await this.dequeue()) !== null && processed < 10) {
        await this.processTask(task);
        processed++;
      }
      
      // Schedule next alarm if more tasks
      const queue = await this.ctx.storage.get<Task[]>("queue") || [];
      if (queue.length > 0) {
        await this.ctx.storage.setAlarm(Date.now() + 1000);
      }
      
    } finally {
      this.processing = false;
    }
  }
  
  async processTask(task: Task): Promise<void> {
    console.log(`Processing task ${task.id} of type ${task.type}`);
    
    // Actual task execution logic
    switch (task.type) {
      case "elicitation":
        await this.runElicitation(task.payload);
        break;
      case "implementation":
        await this.runImplementation(task.payload);
        break;
      default:
        console.warn(`Unknown task type: ${task.type}`);
    }
  }
  
  async runElicitation(payload: any): Promise<void> {
    // AI agent execution
  }
  
  async runImplementation(payload: any): Promise<void> {
    // AI agent execution
  }
  
  async fetch(request: Request): Promise<Response> {
    const url = new URL(request.url);
    
    if (url.pathname === "/enqueue" && request.method === "POST") {
      const task = await request.json<Task>();
      await this.enqueue(task);
      return Response.json({ success: true });
    }
    
    if (url.pathname === "/status") {
      const queue = await this.ctx.storage.get<Task[]>("queue") || [];
      return Response.json({
        queueLength: queue.length,
        processing: this.processing
      });
    }
    
    return new Response("Not Found", { status: 404 });
  }
}

// Worker that uses the queue
export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const queueId = env.TASK_QUEUE.idFromName("main-queue");
    const queue = env.TASK_QUEUE.get(queueId);
    
    return queue.fetch(request);
  }
};

WebSocket Real-time Updates

typescript

export class RealtimeUpdates extends DurableObject {
  private sessions: Map<string, WebSocket> = new Map();
  
  async fetch(request: Request): Promise<Response> {
    if (request.headers.get("Upgrade") !== "websocket") {
      return new Response("Expected WebSocket", { status: 426 });
    }
    
    const pair = new WebSocketPair();
    const [client, server] = [pair[0], pair[1]];
    
    const sessionId = crypto.randomUUID();
    
    server.accept();
    this.sessions.set(sessionId, server);
    
    server.addEventListener("message", async (event) => {
      const message = JSON.parse(event.data as string);
      
      if (message.type === "subscribe") {
        // Subscribe to task updates
        await this.subscribeToTask(sessionId, message.taskId);
      }
    });
    
    server.addEventListener("close", () => {
      this.sessions.delete(sessionId);
    });
    
    return new Response(null, {
      status: 101,
      webSocket: client,
    });
  }
  
  async subscribeToTask(sessionId: string, taskId: string) {
    // Store subscription
    const subscriptions = await this.ctx.storage.get<Map<string, Set<string>>>("subscriptions") || new Map();
    
    if (!subscriptions.has(taskId)) {
      subscriptions.set(taskId, new Set());
    }
    
    subscriptions.get(taskId)!.add(sessionId);
    await this.ctx.storage.put("subscriptions", subscriptions);
  }
  
  async broadcastTaskUpdate(taskId: string, update: any) {
    const subscriptions = await this.ctx.storage.get<Map<string, Set<string>>>("subscriptions") || new Map();
    const subscribers = subscriptions.get(taskId) || new Set();
    
    const message = JSON.stringify({
      type: "task-update",
      taskId,
      update
    });
    
    for (const sessionId of subscribers) {
      const socket = this.sessions.get(sessionId);
      if (socket) {
        socket.send(message);
      }
    }
  }
}

Service Binding for Microservices

typescript

// auth-service/src/index.ts
import { WorkerEntrypoint } from "cloudflare:workers";

export class AuthService extends WorkerEntrypoint<Env> {
  async verifyToken(token: string): Promise<User | null> {
    // Verify JWT token
    const payload = await this.decodeJWT(token);
    
    if (!payload) return null;
    
    return {
      id: payload.sub,
      email: payload.email,
      role: payload.role
    };
  }
  
  async createToken(userId: string): Promise<string> {
    // Generate JWT
    return this.signJWT({ sub: userId });
  }
  
  private async decodeJWT(token: string): Promise<any> {
    // JWT verification logic
  }
  
  private async signJWT(payload: any): Promise<string> {
    // JWT signing logic
  }
}

export default AuthService;

// api-service/src/index.ts
export interface Env {
  AUTH: Service<AuthService>;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const token = request.headers.get("Authorization")?.replace("Bearer ", "");
    
    if (!token) {
      return new Response("Unauthorized", { status: 401 });
    }
    
    // Call auth service via RPC
    const user = await env.AUTH.verifyToken(token);
    
    if (!user) {
      return new Response("Invalid token", { status: 401 });
    }
    
    return Response.json({ user });
  }
};

Summary & Recommendations for MonoTask

Architecture Mapping

MonoTask Component	Cloudflare Service	Notes
Dashboard API	Workers (Hono framework)	HTTP endpoints, REST API
Daemon/Queue	Durable Objects + Queues	Task queue management, state machine
AI Agents	Workers + Workflows	Agent execution with state persistence
Database	D1 (SQLite) or external DB	Relational data storage
Session Management	KV	User sessions, cache
WebSocket Updates	Durable Objects + WebSocket	Real-time task updates
Background Jobs	Scheduled Events + Queues	Cron tasks, batch processing
Task State	Durable Objects	State machine coordination

Migration Strategy

Phase 1: API Layer
- Migrate dashboard API to Workers using Hono
- Use D1 for database or keep external PostgreSQL
- KV for session management and caching
- Service bindings for microservices
Phase 2: Queue System
- Implement task queue with Durable Objects
- Use Alarms API for scheduled processing
- Migrate from daemon to Cloudflare Queues
Phase 3: Agent Execution
- Workers for short-running agents (<30s CPU time)
- Workflows for multi-phase agents (elicitation → planning → implementation)
- Durable Objects for agent state coordination
Phase 4: Real-time Features
- WebSocket server with Durable Objects
- Hibernation API for scaling
- Broadcast task updates to connected clients
Phase 5: Background Jobs
- Scheduled events for cron tasks
- Queue consumers for async processing
- Workflows for long-running operations

Performance Considerations

CPU Time: Configure 5-minute limit for AI agent execution
Paid Tier: Required for production usage
Geographic Distribution: Use location hints for Durable Objects
Caching: Aggressive KV caching to reduce database load
Batching: Use Queues for efficient batch processing

Cost Optimization

Free Tier: 100,000 requests/day (development only)
Paid Tier: $5/month + usage
- $0.50 per million requests
- $0.02 per million Durable Object requests
- KV: $0.50/GB storage, $0.50/million reads
- Queues: $0.40 per million operations

Estimated MonoTask costs (moderate usage):

API requests: ~$2-5/month
Durable Objects: ~$5-10/month
KV: ~$1-2/month
Total: ~$10-20/month for moderate usage

Additional Resources

Official Docs: https://developers.cloudflare.com/workers/
Examples: https://developers.cloudflare.com/workers/examples/
Discord: Cloudflare Developers Discord
GitHub: https://github.com/cloudflare/workers-sdk

Research compiled: 2025-10-25
Target system: MonoTask AI Agent Automation Platform
Focus: Migration to Cloudflare Workers for serverless AI agent orchestration

Cloudflare Workers Research ​

Table of Contents ​

Workers Architecture Overview ​

V8 Isolate Model ​

Runtime Environment ​

Request/Response Lifecycle ​

Handler Types ​

Durable Objects for Queue Management ​

Architecture and Consistency Guarantees ​

Defining a Durable Object ​

Storage API ​

In-Memory State vs Persistent Storage ​

Alarms API for Scheduling ​

Concurrency Control ​

Accessing Durable Objects from Workers ​

Queue Implementation Pattern ​

WebSocket Handling for Real-time Updates ​

WebSocketPair API ​

Integration with Durable Objects ​

WebSocket Hibernation API ​

Broadcasting Patterns ​

KV Storage for Session Management ​

API Overview ​

KV API Methods ​

Session Management Pattern ​

Caching Pattern ​

Metadata Pattern ​

List Keys Pattern ​

TTL and Expiration ​

Best Practices ​

Worker-to-Worker Communication ​

Service Bindings Overview ​

RPC vs HTTP Communication ​

RPC Implementation ​

HTTP Service Binding ​

Context Passing with ctx.props ​

TypeScript Type Safety ​

Performance Characteristics ​

Environment Variables and Secrets ​

Configuration via env Parameter ​

wrangler.toml Configuration ​

Secrets Management ​

Best Practices ​

Scheduling and Cron Triggers ​

Scheduled Handler Implementation ​

Cron Configuration ​

Integration with Queues ​

Integration with Workflows ​

Local Testing ​

Use Cases ​

Cloudflare Queues ​

Producer API ​

Consumer API ​

Message Structure ​

Configuration ​

Retry Pattern with Exponential Backoff ​

Dead Letter Queue ​

Limits ​

Queues vs Durable Objects ​

Workflows for Durable Execution ​

Key Differences from Workers ​

Workflow Definition ​

Triggering Workflows ​

Workflow Events (Human-in-the-Loop) ​

State Persistence ​

Use Cases for AI Agents ​

Error Handling and Logging ​

Console Logging ​

Error Handling Patterns ​

ctx.passThroughOnException() ​

ctx.waitUntil() for Background Tasks ​

Workers Logpush ​

Tail Workers (Beta) ​

Monitoring Best Practices ​

Performance Limits and Quotas ​

Worker Execution Limits ​

Request Limits ​

Durable Objects Limits ​

KV Limits ​

Queue Limits ​

Cloudflare Workers Research

Table of Contents

Workers Architecture Overview

V8 Isolate Model

Runtime Environment

Request/Response Lifecycle

Handler Types

Durable Objects for Queue Management

Architecture and Consistency Guarantees

Defining a Durable Object

Storage API

In-Memory State vs Persistent Storage

Alarms API for Scheduling

Concurrency Control

Accessing Durable Objects from Workers

Queue Implementation Pattern

WebSocket Handling for Real-time Updates

WebSocketPair API

Integration with Durable Objects

WebSocket Hibernation API

Broadcasting Patterns

KV Storage for Session Management

API Overview

KV API Methods

Session Management Pattern

Caching Pattern

Metadata Pattern

List Keys Pattern

TTL and Expiration

Best Practices

Worker-to-Worker Communication

Service Bindings Overview

RPC vs HTTP Communication

RPC Implementation

HTTP Service Binding

Context Passing with ctx.props

TypeScript Type Safety

Performance Characteristics

Environment Variables and Secrets

Configuration via env Parameter

wrangler.toml Configuration

Secrets Management

Best Practices

Scheduling and Cron Triggers

Scheduled Handler Implementation

Cron Configuration

Integration with Queues

Integration with Workflows

Local Testing

Use Cases

Cloudflare Queues

Producer API

Consumer API

Message Structure

Configuration

Retry Pattern with Exponential Backoff

Dead Letter Queue

Limits

Queues vs Durable Objects

Workflows for Durable Execution

Key Differences from Workers

Workflow Definition

Triggering Workflows

Workflow Events (Human-in-the-Loop)

State Persistence

Use Cases for AI Agents

Error Handling and Logging

Console Logging

Error Handling Patterns

ctx.passThroughOnException()

ctx.waitUntil() for Background Tasks

Workers Logpush

Tail Workers (Beta)

Monitoring Best Practices

Performance Limits and Quotas

Worker Execution Limits

Request Limits

Durable Objects Limits

KV Limits

Queue Limits