Cloudflare Workers: Queues for Async Processing

TL;DR: Cloudflare Queues is a global message queue service for Workers that handles async processing, load leveling, and retry logic. This guide covers queue configuration, producer/consumer patterns, batch processing, and dead letter queues.

Introduction

Async processing decouples request handling from expensive operations. Instead of processing an email send during an HTTP request, you queue the job and handle it separately. For more on async patterns with Durable Objects for real-time coordination, see our Cloudflare Workers Durable Objects guide. Queues provide at-least-once delivery, automatic retries, and configurable concurrency.

Queue Configuration

# wrangler.jsonc
{
  "queues": {
    "producers": ["email-queue"],
    "consumers": {
      "email-queue": {
        "max_batch_size": 10,
        "max_batch_timeout": 5,
        "max_retries": 3,
        "dead_letter_queue": "email-queue-dlq"
      }
    }
  }
}

Producer Pattern

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const body = await request.json()
    await env.EMAIL_QUEUE.send({
      to: body.email,
      template: 'welcome',
      data: { name: body.name },
    })
    return new Response('Queued', { status: 202 })
  },
}

Consumer Handler

export default {
  async queue(batch: MessageBatch<EmailMessage>, env: Env): Promise<void> {
    for (const message of batch.messages) {
      try {
        await sendEmail(message.body)
        message.ack()
      } catch (error) {
        message.retry({ delaySeconds: 60 })
      }
    }
  },
}

Queue Use Cases

Conclusion

Queues provide reliable async processing for Workers applications. Use them for any operation that doesn't need to complete during the HTTP request — email sending, image processing, data synchronization, and report generation. For scheduling regular queue-producing tasks, combine Queues with Cloudflare Workers Cron Triggers. And to track queue performance, leverage the Cloudflare Workers Analytics Engine for monitoring throughput and error rates.