Azure – Scaling failed: "Not enough available reserved instance servers..."

Question

Hi everyone,

I’m running into an issue during an automated scale-out process in Azure, and I could use some help understanding what's going on.

This morning, when trying to scale up a set of app services instances (not reserved instances), we received the following error message:

"Not enough available reserved instance servers to satisfy this request. Currently 2 instances are available. If you are changing instance size you can reserve up to 2 instances at this moment. If you are increasing instance count then you can add extra 2 instances at this moment. Please get available machines and retry later."

A few things to clarify:

We’re not using reserved instances.

The scaling was fully automated and failed unexpectedly.

We were simply trying to add more instances of the same size (no resize involved).

Questions:

1. Does this actually mean capacity in the region/zone was temporarily exhausted? How come?

Is there a way to check available capacity ahead of time or get alerts before this happens?

Any recommendations to prevent this kind of failure in future automated scale-outs?

Thanks in advance for any insights or suggestions!