How long to wait for a response to a quota increase reply?

The timeline for receiving a response to a quota increase request can vary, especially when additional information is provided after an initial denial. While AWS aims to provide an initial response within 24 hours, the actual resolution time can be longer, particularly for more complex cases or larger increase requests.

When you submit a quota increase request, smaller increases are often automatically approved. However, larger requests or those requiring more scrutiny are submitted to AWS Support for review. These requests take time to process, approve, and deploy.

In your case, since you've provided additional information after an initial denial, it's likely that your request is being reviewed more thoroughly. The AWS Support team needs to carefully consider each request to prevent misuse of their systems.

It's important to note that quota increase requests don't receive priority support. The process can take a couple of days for the increase to take effect, even after approval. In some cases, if AWS needs additional information from you, it might take longer to resolve your request.

Given that it's been about 20 hours since your reply, it's still within the typical response window. However, if your request is urgent, you might want to check the AWS Support console to track the status of your request. You can also consider contacting AWS Support directly to inquire about the status, emphasizing the time-sensitive nature of your project.

Remember that AWS might not be able to grant your request if your use case doesn't align with their policies, even with the additional explanation provided. If you haven't heard back within 24-48 hours, it would be appropriate to follow up on your request.
Sources
Request a quota increase - AWS Control Tower
Requesting a quota increase - Service Quotas
AWS service quotas - AWS General Reference
Quotas for AWS End User Messaging SMS - AWS End User Messaging SMS