# Amazon SQS standard queues
Amazon SQS provides standard queues as the default queue type, supporting a nearly unlimited number of API calls per second for actions like [https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_SendMessage.html](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_SendMessage.html), [https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_ReceiveMessage.html](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_ReceiveMessage.html), and [https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_DeleteMessage.html](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_DeleteMessage.html). Standard queues ensure at-least-once message delivery, but due to the highly distributed architecture, more than one copy of a message might be delivered, and messages may occasionally arrive out of order. Despite this, standard queues make a best-effort attempt to maintain the order in which messages are sent.
When you send a message using `SendMessage`, Amazon SQS redundantly stores the message in multiple availability zones (AZs) before acknowledging it. This redundancy ensures that no single computer, network, or AZ failure can render the messages inaccessible.
You can create and configure queues using the Amazon SQS console. For detailed instructions, see [Creating a standard queue using the Amazon SQS console](creating-sqs-standard-queues.md#step-create-standard-queue). For Java-specific examples, see [Amazon SQS Java SDK examples](sqs-java-tutorials.md).
**Use cases for standard queues**
Standard message queues are suitable for various scenarios, as long as your application can handle messages that might arrive more than once or out of order. Examples include:
+ **Decoupling live user requests from intensive background work** – Users can upload media while the system resizes or encodes it in the background.
+ **Allocating tasks to multiple worker nodes** – For example, handling a high volume of credit card validation requests.
+ **Batching messages for future processing** – Scheduling multiple entries to be added to a database at a later time.
For information on quotas related to standard queues, see [Amazon SQS standard queue quotas](quotas-queues.md).
For best practices of working with standard queues, see [Amazon SQS best practices](sqs-best-practices.md).
# Amazon SQS at-least-once delivery
Amazon SQS stores copies of your messages on multiple servers for redundancy and high availability. On rare occasions, one of the servers that stores a copy of a message might be unavailable when you receive or delete a message.
If this occurs, the copy of the message isn't deleted on the server that is unavailable, and you might get that message copy again when you receive messages. Design your applications to be *idempotent* (they should not be affected adversely when processing the same message more than once).
# Amazon SQS queue and message identifiers
This topic describes the identifiers of standard and FIFO queues. These identifiers can help you find and manipulate specific queues and messages.
## Identifiers for Amazon SQS standard queues
For more information about the following identifiers, see the *[Amazon Simple Queue Service API Reference](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/)*.
### Queue name and URL
When you create a new queue, you must specify a queue name unique for your AWS account and region. Amazon SQS assigns each queue you create an identifier called a *queue URL* that includes the queue name and other Amazon SQS components. Whenever you want to perform an action on a queue, you provide its queue URL.
The following is the queue URL for a queue named `MyQueue` owned by a user with the AWS account number `123456789012`.
```
https://sqs.us-east-2.amazonaws.com/123456789012/MyQueue
```
You can retrieve the URL of a queue programmatically by listing your queues and parsing the string that follows the account number. For more information, see `[ListQueues](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_ListQueues.html)`.
### Message ID
Each message receives a system-assigned *message ID* that Amazon SQS returns to you in the `[SendMessage](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_SendMessage.html)` response. This identifier is useful for identifying messages. The maximum length of a message ID is 100 characters.
### Receipt handle
Every time you receive a message from a queue, you receive a *receipt handle* for that message. This handle is associated with the action of receiving the message, not with the message itself. To delete the message or to change the message visibility, you must provide the receipt handle (not the message ID). Thus, you must always receive a message before you can delete it (you can't put a message into the queue and then recall it). The maximum length of a receipt handle is 1,024 characters.
**Important**
If you receive a message more than once, each time you receive it, you get a different receipt handle. You must provide the most recently received receipt handle when you request to delete the message (otherwise, the message might not be deleted).
The following is an example of a receipt handle broken across three lines.
```
MbZj6wDWli+JvwwJaBV+3dcjk2YW2vA3+STFFljTM8tJJg6HRG6PYSasuWXPJB+Cw
Lj1FjgXUv1uSj1gUPAWV66FU/WeR4mq2OKpEGYWbnLmpRCJVAyeMjeU5ZBdtcQ+QE
auMZc8ZRv37sIW2iJKq3M9MFx1YvV11A2x/KSbkJ0=
```