Amazon SQS: The same message is consumed by two current consumers

Amazon does not guarantee exactly once delivery with SQS. They guarantee "at least once" delivery. This is addressed in the FAQ https://aws.amazon.com/sqs/faqs/

You have to keep this in mind and design your system to gracefully handle duplicate message delivery.

This is possible now with FIFO SQS queues. You can make sure exactly one client receives the message and then delete it while the message is in-flight

More information here:

https://aws.amazon.com/about-aws/whats-new/2016/11/amazon-sqs-introduces-fifo-queues-with-exactly-once-processing-and-lower-prices-for-standard-queues/