1# Cloudflare Workers
2 
3Expert guidance for building, deploying, and optimizing Cloudflare Workers applications.
4 
5## Overview
6 
7Cloudflare Workers run on V8 isolates (NOT containers/VMs):
8- Extremely fast cold starts (< 1ms)
9- Global deployment across 300+ locations
10- Web standards compliant (fetch, URL, Headers, Request, Response)
11- Support JS/TS, Python, Rust, and WebAssembly
12 
13**Key principle**: Workers use web platform APIs wherever possible for portability.
14 
15## Module Worker Pattern (Recommended)
16 
17```typescript
18export default {
19  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
20    return new Response('Hello World!');
21  },
22};
23```
24 
25**Handler parameters**:
26- `request`: Incoming HTTP request (standard Request object)
27- `env`: Environment bindings (KV, D1, R2, secrets, vars)
28- `ctx`: Execution context (`waitUntil`, `passThroughOnException`)
29 
30## Essential Commands
31 
32```bash
33npx wrangler dev                    # Local dev
34npx wrangler dev --remote           # Remote dev (actual resources)
35npx wrangler deploy                 # Production
36npx wrangler deploy --env staging   # Specific environment
37npx wrangler tail                   # Stream logs
38npx wrangler secret put API_KEY     # Set secret
39```
40 
41## When to Use Workers
42 
43- API endpoints at the edge
44- Request/response transformation
45- Authentication/authorization layers
46- Static asset optimization
47- A/B testing and feature flags
48- Rate limiting and security
49- Proxy/routing logic
50- WebSocket applications
51 
52## Quick Start
53 
54```bash
55npm create cloudflare@latest my-worker -- --type hello-world
56cd my-worker
57npx wrangler dev
58```
59 
60## Handler Signatures
61 
62```typescript
63// HTTP requests
64async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response>
65 
66// Cron triggers
67async scheduled(event: ScheduledEvent, env: Env, ctx: ExecutionContext): Promise<void>
68 
69// Queue consumer
70async queue(batch: MessageBatch, env: Env, ctx: ExecutionContext): Promise<void>
71 
72// Tail consumer
73async tail(events: TraceItem[], env: Env, ctx: ExecutionContext): Promise<void>
74```
75 
76## Resources
77 
78**Docs**: https://developers.cloudflare.com/workers/  
79**Examples**: https://developers.cloudflare.com/workers/examples/  
80**Runtime APIs**: https://developers.cloudflare.com/workers/runtime-apis/
81 
82## In This Reference
83 
84- [Configuration](./configuration.md) - wrangler.jsonc setup, bindings, environments
85- [API](./api.md) - Runtime APIs, bindings, execution context
86- [Patterns](./patterns.md) - Common workflows, testing, optimization
87- [Frameworks](./frameworks.md) - Hono, routing, validation
88- [Gotchas](./gotchas.md) - Common issues, limits, troubleshooting
89 
90## Reading Order
91 
92| Task | Start With | Then Read |
93|------|------------|-----------|
94| First Worker | README → Configuration → API | Patterns |
95| Add framework | Frameworks | Configuration (bindings) |
96| Add storage/bindings | Configuration → API (binding usage) | See Also links |
97| Debug issues | Gotchas | API (specific binding docs) |
98| Production optimization | Patterns | API (caching, streaming) |
99| Type safety | Configuration (TypeScript) | Frameworks (Hono typing) |
100 
101## See Also
102 
103- [KV](../kv/README.md) - Key-value storage
104- [D1](../d1/README.md) - SQL database
105- [R2](../r2/README.md) - Object storage
106- [Durable Objects](../durable-objects/README.md) - Stateful coordination
107- [Queues](../queues/README.md) - Message queues
108- [Wrangler](../wrangler/README.md) - CLI tool reference
109