How do I request an exception to reduce throttling in AWS Polly to have more requests per second

Your AWS account has default quotas, formerly referred to as limits, for each AWS service. You can request an increase through the AWS Support Center Console by following the instructions here:

https://docs.aws.amazon.com/awssupport/latest/user/create-service-quota-increase.html

Unless otherwise noted, each quota is Region-specific. You can request increases for some quotas, and other quotas cannot be increased.