How to migrate a domain name attached to Frontdoor Premium to another Frontdoor Standard

Question

We have a container app that is served by a Frontdoor Premium.

We would like to move to downgrade to Frontdoor Standard.

How to do it without any downtime?

Our bet was to move our CNAME to our Container app, move the custom domain from Premium to Standard Frontdoor and switch the CNAME back to the new Frontdoor Standard.

Unfortunately this does not work since we are not able to create any custom name on our Container App before the CNAME is actually set on the DNS.
Doing this will lead to a downtime because of the DNS cache.

Is there any best practice how to solve such situation?

Answer 1

@91971187 ,

Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.

Looking at your setup, you would definitely need a migration window/downtime to achieve this.

I take it that your intention is to

1. Remove the custom domain from AFD Premium
   1. This way, you work around the limitation of
      
2. Add a CNAME to point to the actual Origin (Container Apps)
   1. From the docs, Custom domain names and BYOC in Azure Container Apps
   2. I see you are required to add a CNAME record for this validation to be done
3. Finally, validate the domain in AFD Standard and add a CNAME record.

In step #2, I don't see what the blocker here is.

• If you are worried about DNS Cache, you can update the TTL to a minimal value
• The general limit is 7 days, so after 7 days all the DNS Servers world wide would have updated your DNS with the new TTL value (which is now a minimum value)
• Moreover, even if you were to add a custom domain to the Container App without CNAME hypothetically- you must understand that DNS will not resolve to the Container Apps IP and just having a custom domain on the Container App would not help anyways.
  • i.e., without CNAME, no traffic would ever reach the Container App in the first place.

Again, you are hitting a product design consideration,

• 
• And so, I would suggest you plan the migration with a maintenance window.

Hope this adds more clarity

Cheers,

Kapil