Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.
I understand that you would like to know more about using Azure Private Link behind Azure Front Door.
I believe this is the official how to documentation : Connect Azure Front Door Premium to an internal load balancer origin with Private Link
As long as a PaaS or Computer service supports being in the backend pool of an Internal Load Balancer, this configuration should work.
I wouldn't say this is a official documentation from Microsoft for connecting Front Door to an internal ACA environment's internal Load Balancer, as it would be challenging to provide such configuration for every PaaS service that supports ILB.
However, we can guarantee Internal Load Balancer is a stable resource and Standard LB has 99.99% SLA
Also, Refer : Azure SLA
Kindly let us know if this helps or you need further assistance on this issue.
Thanks,
Kapil
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