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SQS (Simple Queue Service)


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Amazon SQS is a fully managed message queuing service that enables you to decouple and scale microservices, distributed systems, and serverless applications.

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Queue Types​

Standard Queue​

  • Default queue type
  • Nearly unlimited throughput (unlimited number of transactions per second)
  • At-least-once delivery (a message is delivered at least once, but occasionally more than one copy is delivered)
  • Best-effort ordering (messages are generally delivered in the order they are sent, but ordering is not guaranteed)

FIFO Queue​

  • High throughput (up to 300 messages per second without batching, 3000 with batching)
  • Exactly-once processing (a message is delivered once and remains available until a consumer processes and deletes it)
  • First-in-first-out delivery (the order in which messages are sent and received is strictly preserved)
  • FIFO queue names must end with the .fifo suffix
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Message Lifecycle​

  • A producer sends a message to the queue
  • A consumer retrieves the message from the queue (the message remains in the queue while being processed)
  • The consumer deletes the message from the queue after processing it
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Visibility Timeout​

  • Period of time during which SQS prevents other consumers from receiving and processing a message that has already been retrieved
  • Default: 30 seconds
  • Minimum: 0 seconds
  • Maximum: 12 hours
  • If the consumer does not delete the message within the visibility timeout, the message becomes available again for other consumers
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Message Retention​

  • Duration that a message is retained in the queue
  • Default: 4 days
  • Minimum: 1 minute
  • Maximum: 14 days
  • After the retention period, the message is automatically deleted
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Dead-Letter Queue​

  • A queue that other queues (source queues) can target for messages that were not successfully processed
  • Useful for isolating and debugging problematic messages
  • Configured via a redrive policy that specifies the source queue, the dead-letter queue, and the maximum number of receives before a message is moved to the dead-letter queue
  • The dead-letter queue must be the same type as the source queue (Standard or FIFO)
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Delay Queue​

  • Postpones the delivery of new messages for a specified number of seconds
  • Messages sent to a delay queue remain invisible to consumers during the delay period
  • Default: 0 seconds
  • Maximum: 15 minutes
  • For Standard queues, changing the delay setting does not affect messages already in the queue
  • For FIFO queues, per-message delays are not supported
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Long Polling​

  • Reduces the number of empty responses by allowing SQS to wait until a message is available before sending a response
  • Helps reduce costs by eliminating the number of empty receives
  • Enabled by setting the ReceiveMessageWaitTimeSeconds attribute to a value greater than 0 (maximum 20 seconds)
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Encryption​

  • Server-side encryption (SSE) protects the contents of messages in queues using SQS-managed encryption keys (SSE-SQS) or AWS KMS keys (SSE-KMS)
  • Encryption at rest is applied to the message body, but not to the queue metadata, message metadata, or per-queue metrics
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