aws sqs queue types

The primary difference between queue types is how they handle the ordering of messages.

Two types of queue

1. Standard queues are the default - which provide "best-effort" ordering
2. FIFO (first-in-first-out) - ordering of messages is strictly preserved

Standard queues

• Nearly unlimited number of transactions per second
• Guarantees that a message is delivered at least once
• Best-effort ordering - provides a "generally delivered" in the same order as they're sent
  • Due to the highly distributed system, some may be delivered multiple times or
  in the wrong order

FIFO queues

• First-in-first-out delivery - order messages are received is strictly preserved
• Exactly-once processing - a message is delivered once and remains available

until a consumer processes and deletes it. Duplicates are not introduced.

• 300 transactions per second limit
  • FIFO queues are limited to 300 TPS, but have all the capabilities of a standard queue

Exam tips

• Standard queue:
  • Best-effort ordering
  • Message delivered at least once
  • Occasional duplicates
  • Default queue type
• FIFO queue:
  • First-in-first-out message order is strictly preserved
  • Messages are delivered once
  • No duplicates