> ## Documentation Index
> Fetch the complete documentation index at: https://upstash.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Queues

The queue concept in QStash allows ordered delivery (FIFO).
See the [API doc](/qstash/api-reference/queues/list-queues) for the full list of related Rest APIs.
Here we list common use cases for Queue and how to use them.

## Ordered Delivery

With Queues, the ordered delivery is guaranteed by default.
This means:

* Your messages will be queued without blocking the REST API and sent one by one in FIFO order. Queued means [CREATED](/qstash/howto/debug-logs) event will be logged.
* The next message will wait for retries of the current one if it can not be delivered because your endpoint returns non-2xx code.
  In other words, the next message will be [ACTIVE](/qstash/howto/debug-logs) only after the last message is either [DELIVERED](/qstash/howto/debug-logs) or
  [FAILED](/qstash/howto/debug-logs).
* Next message will wait for [callbacks](/qstash/features/callbacks#what-is-a-callback) or [failure callbacks](/qstash/features/callbacks#what-is-a-failure-callback) to finish.

<CodeGroup>
  ```bash cURL theme={"system"}
  curl -XPOST -H 'Authorization: Bearer XXX' \
              -H "Content-type: application/json" \
    'https://qstash.upstash.io/v2/enqueue/my-queue/https://example.com' -d '{"message":"Hello, World!"}'
  ```

  ```typescript TypeScript theme={"system"}
  const client = new Client({ token: "<QSTASH_TOKEN>" });

  const queue = client.queue({
    queueName: "my-queue"
  })

  await queue.enqueueJSON({
    url: "https://example.com",
    body: {
      "Hello": "World"
    }
  })
  ```

  ```python Python theme={"system"}
  from qstash import QStash

  client = QStash("<QSTASH_TOKEN>")
  client.message.enqueue_json(
      queue="my-queue",
      url="https://example.com",
      body={
          "Hello": "World",
      },
  )
  ```
</CodeGroup>

## Controlled Parallelism

<Warning>
  For the parallelism limit, we introduced an easier and less limited API with publish.
  Please check the [Flow Control](/qstash/features/flowcontrol) page for the detailed information.

  Setting parallelism with queues will be deprecated at some point.
</Warning>

To ensure that your endpoint is not overwhelmed and also you want more than one-by-one delivery for better throughput,
you can achieve controlled parallelism with queues.

By default, queues have parallelism 1.
Depending on your [plan](https://upstash.com/pricing/qstash), you can configure the parallelism of your queues as follows:

<CodeGroup>
  ```bash cURL theme={"system"}
  curl -XPOST https://qstash.upstash.io/v2/queues/ \
    -H "Authorization: Bearer <token>" \
    -H "Content-Type: application/json" \
    -d '{
      "queueName": "my-queue", 
      "parallelism": 5,
    }'
  ```

  ```typescript TypeScript theme={"system"}
  const client = new Client({ token: "<QSTASH_TOKEN>" });

  const queue = client.queue({
    queueName: "my-queue"
  })

  await queue.upsert({
    parallelism: 1,
  })
  ```

  ```python Python theme={"system"}
  from qstash import QStash

  client = QStash("<QSTASH_TOKEN>")
  client.queue.upsert("my-queue", parallelism=5)
  ```
</CodeGroup>

After that, you can use the `enqueue` path to send your messages.

<CodeGroup>
  ```bash cURL theme={"system"}
  curl -XPOST -H 'Authorization: Bearer XXX' \ 
              -H "Content-type: application/json" \
    'https://qstash.upstash.io/v2/enqueue/my-queue/https://example.com' -d '{"message":"Hello, World!"}'
  ```

  ```typescript TypeScript theme={"system"}
  const client = new Client({ token: "<QSTASH_TOKEN>" });

  const queue = QStashClient.queue({
    queueName: "my-queue"
  })

  await queue.enqueueJSON({
    url: "https://example.com",
    body: {
      "Hello": "World"
    }
  })
  ```

  ```python Python theme={"system"}
  from qstash import QStash

  client = QStash("<QSTASH_TOKEN>")
  client.message.enqueue_json(
      queue="my-queue",
      url="https://example.com",
      body={
          "Hello": "World",
      },
  )
  ```
</CodeGroup>

You can check the parallelism of your queues with the following API:

<CodeGroup>
  ```bash cURL theme={"system"}
  curl https://qstash.upstash.io/v2/queues/my-queue \
    -H "Authorization: Bearer <token>"
  ```

  ```typescript TypeScript theme={"system"}
  const client = new Client({ token: "<QSTASH_TOKEN>" });

  const queue = client.queue({
    queueName: "my-queue"
  })

  const res = await queue.get()
  ```

  ```python Python theme={"system"}
  from qstash import QStash

  client = QStash("<QSTASH_TOKEN>")
  client.queue.get("my-queue")
  ```
</CodeGroup>