Queues

Learning Focus

By the end of this lesson you will understand how Cloudflare Queues enable asynchronous processing between Workers and their free-tier limits.

What Are Cloudflare Queues?

Cloudflare Queues is a message broker that allows Workers to send and consume messages asynchronously. Instead of processing everything in a single request, you can offload work to a queue and process it later in a separate Worker.

flowchart LR
    PRODUCER["Producer Worker\n(Handles request)"] -->|"Send message"| QUEUE["Queue\n(Message Buffer)"]
    QUEUE -->|"Batch delivery"| CONSUMER["Consumer Worker\n(Background processing)"]

    style QUEUE fill:#7c3aed,color:#fff,stroke:#6d28d9
    style PRODUCER fill:#f6821f,color:#fff,stroke:#e5711e
    style CONSUMER fill:#16a34a,color:#fff,stroke:#15803d

Use Cases

Use Case	Description
Email sending	Queue email tasks, process in background
Image processing	Resize/optimize images asynchronously
Webhook delivery	Retry failed webhook deliveries
Log aggregation	Batch and process log entries
Data pipeline	Process data transformations step by step

Free Tier

Resource	Free Plan
Messages sent	1 million per month
Messages read	1 million per month
Queues	100

Basic Example

Producer (Sends Messages)

src/producer.ts

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const body = await request.json() as any;

    // Send a message to the queue
    await env.MY_QUEUE.send({
      type: "email",
      to: body.email,
      subject: "Welcome!",
      body: "Thanks for signing up.",
    });

    return Response.json({ status: "queued" });
  },
};

Consumer (Processes Messages)

src/consumer.ts

export default {
  async queue(batch: MessageBatch, env: Env): Promise<void> {
    for (const message of batch.messages) {
      console.log(`Processing: ${JSON.stringify(message.body)}`);

      // Process the message (e.g., send email, resize image)
      // ...

      // Acknowledge successful processing
      message.ack();
    }
  },
};

wrangler.toml

name = "my-worker"
main = "src/producer.ts"

[[queues.producers]]
queue = "my-queue"
binding = "MY_QUEUE"

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

Key Takeaways

• Queues enable asynchronous processing between Workers.
• Free tier: 1M messages sent/read per month.
• Messages are delivered in batches for efficiency.
• Ideal for background tasks, retries, and data pipelines.

What's Next

• Continue to Secrets Store and Version Management to learn about secure configuration and deployment versioning.