I am using a SNS to send out notifications to SQS in another AWS account. There is a DLQ configured to this SQS listener for processing failure of messages in SQS. Is it feasible to use same DLQ for handling SNS subscription failures as well?
While you certainly can use the same SQS as a DLQ for both the SNS topic and the SQS subscription, doing so might not be advisable. You'd be writing two different kinds of messages to the same queue, which might need different types of processing. The DLQ queue would also need a wider set of permissions to accommodate multiple writers. I would recommend using separate DLQs for the two different use cases.