backup plan when cloud infra failed

When the whole deployment infra is based on the cloud service, and the AWS experienced outrage at a region, for example,

In this scenario, need to prepare:

• migrate all the service on multiple regions (all the service from scratch)

• make sure data receiving always work; so that even they might not be able to get the processed data, they are able to get it after the service is recovered without resending the data.

• identify the issue and alert customers before they noticed it.

What event will trigger a notification?