Are AWS SQS queues isolated from each other?

Question

Say that I have two separate services, A and B, with SQS queues that are both subscribed to SNS topic "topic-foo". Then I publish a message m1 to the SNS topic "topic-foo".

If the SQS queue owned by service A (sqs-A) sees message m1 and processes it (ie pops it off the queue and processes the message so that it's no longer on sqs-A), will I still be guaranteed that the separate SQS queue owned by service B (sqs-B) will always be able to see and process message m1? (in other words, does AWS SNS publishing guarantee multiple delivery to SQS queues and isolation of separate SQS queue processing?)

Answer 1

In your situation, you have two SQS queues, each one is subscribed to an SNS topic.

In this case, when you send a message to the SNS topic, an item is added to each of the SQS queues. The two queues are distinct and independent, so processing the item in one queue will not affect the item in the other queue.

This has nothing to do with SNS and is purely because your two SQS queues are two separate SQS queues. The fact that SNS is publishing to them doesn't change how the queues behave.