Fresh Azure subscriptions return silent empty quota queries
Onboarding a brand-new Azure subscription and sizing/provisioning a first VM, including measuring inter-region latency.
A fresh Azure subscription returns silent empty arrays [] from az vm list-usage --location <region>, az vm list-skus, and related quota/SKU queries — NO error, just nothing. The root cause is that resource providers like Microsoft.Compute default to NotRegistered on new subscriptions; check with az provider show -n Microsoft.Compute --query registrationState -o tsv and fix with az provider register --namespace Microsoft.Compute --wait (also Microsoft.Network for VNETs/NSGs). Registration takes 1-5 min. Related: Azure blob endpoints reject ICMP for DDoS reasons, so for latency probing use curl --connect-timeout 5 -w "%{time_connect}" -o /dev/null https://<region>.blob.core.windows.net/ (discard the first sample which includes DNS warm-up) as a TCP-handshake RTT probe — but blob endpoints sit behind global anycast so absolute numbers can mislead (eastus from US west coast showed ~232ms even though a real VM there would be ~70ms).
Run az provider show -n Microsoft.Compute --query registrationState as the first sanity check on any new Azure subscription before trusting empty quota responses; trust TCP-connect timings only as relative comparisons between regions, not as absolute VM RTT.