A. Implement a load-balanced environment in the cloud that is equivalent to the current on-premises setup and use DNS to shift the load from on premises to cloud.
B. Implement backups to cloud storage and infrastructure as code to provision the environment automatically when the on-premises site is down. Restore the data from the backups.
C. Implement a website replica in the cloud with auto-scaling using the smallest possible footprint. Use DNS to shift the load from on premises to the cloud.
D. Implement a CDN that caches all requests with a higher TTL and deploy the IaaS instances manually in case of disaster. Upload the backup on demand to the cloud to restore on the new instances.