Handlers

The default export is a Worker. Add only the handlers you need.

fetch — HTTP

export default {
  async fetch(request, env, ctx) {
    const url = new URL(request.url)
    const path = url.pathname.replace(/\/+$/, '') || '/'

    if (path === '/' && request.method === 'GET') {
      return new Response('<h1>store</h1>', {
        headers: { 'content-type': 'text/html; charset=utf-8' },
      })
    }

    if (path === '/api/products' && request.method === 'GET') {
      const { results } = await env.DB.prepare(
        'select id, name, price_cents from products where active = 1',
      ).all()
      return Response.json({ products: results })
    }

    return Response.json({ error: 'not found' }, { status: 404 })
  },
}

Gateway routes by Host (Preview). The Worker still sees pathname /api/products from / (no /{project}/{version} prefix). Use relative links in HTML.

ctx.waitUntil(promise) is available as celld implements it.

scheduled — Cron

wrangler:

"triggers": { "crons": ["0 * * * *"] }

export default {
  async fetch(request, env) { /* … */ },

  async scheduled(controller, env, ctx) {
    await env.CACHE.put('cron:last-run', String(controller.scheduledTime))
  },
}

Runs only while the version is ready (a live process). Archived versions do not tick. Cron.

Queues — produce from HTTP

wrangler producers + env.QUEUE.send:

await env.FULFILLMENT.send({
  type: 'order.placed',
  order_id: 42,
  at: Date.now(),
})

Producer vs consumer

A queue consumer must export queue(). If that script has no fetch, celld compiles a 404 stub. HTTP fetch + queue() on one module is not the supported cellp pattern — keep a producer Worker for HTTP (dev/examples/queue) and a separate consumer if you need queue().

Queues.

Workflows — class + create

import { WorkflowEntrypoint } from 'cloudflare:workers'

export class OrderReport extends WorkflowEntrypoint {
  async run(event, step) {
    return await step.do('summarize orders', async () => {
      const row = await this.env.DB.prepare(
        'select count(*) as orders from orders',
      ).first()
      return { ...row, generated_at: Date.now() }
    })
  }
}

export default {
  async fetch(request, env) {
    if (new URL(request.url).pathname === '/api/report' && request.method === 'POST') {
      const instance = await env.REPORTS.create({ params: { scope: 'orders' } })
      return Response.json({ id: instance.id })
    }
    return new Response('ok')
  },
}

class_name in wrangler must be OrderReport. Preview versions do not inherit in-flight instances. Workflows.

Durable Objects

export class Counter {
  constructor(state, env) {
    this.state = state
    this.env = env
  }
  async fetch(request) {
    let n = (await this.state.storage.get('n')) ?? 0
    n++
    await this.state.storage.put('n', n)
    return Response.json({ n, version: this.env.VERSION_ID })
  }
}

export default {
  async fetch(request, env) {
    const id = env.COUNTER.idFromName(env.VERSION_ID ?? 'default')
    return env.COUNTER.get(id).fetch(request)
  },
}

Repo: dev/examples/counter. Confirm gaps in celld compat before production use.

Platform keys on env

Always present, read-only: PROJECT_ID, VERSION_ID. Your wrangler vars and Dashboard overrides sit beside them. Env.

Static HTML

You can return new Response(html, { headers: { 'content-type': 'text/html' } }) from fetch, as the commerce storefront does. wrangler assets / Workers Sites work within celld support — see Supported stacks.