If the producer sends a message to an SQS FIFO queue while another message with the same de-duplication ID is in-flight (read by the consumer but not yet committed), will the new message be dropped as duplicated? Or will it be added to the queue as a new message?
According to the documentation, the second (duplicate) message will be dropped if it was sent during a 5-minute window.
It ensures that within a 5-minute deduplication window, only one instance of a message with the same deduplication ID is processed and delivered.
If Amazon SQS has already accepted a message with a specific deduplication ID, any subsequent messages with the same ID will be acknowledged but not delivered to consumers.
And the note:
Amazon SQS continues tracking the deduplication ID even after the message has been received and deleted.