Azure Data Factory Web API call to Azure REST API Slow

I can reproduce this easily.  Call to Azure REST API to publish data to Event Hub using SAS authorization takes few milliseconds from any REST client.

Create Event hub namespace URI and Event Hub Name

Copy the URI and RootManageSharedAccessKey

Create authorization for REST API

https://learn.microsoft.com/en-us/rest/api/eventhub/generate-sas-token#code-try-8

Send data to Event Hub via REST API using Authorization with Postman or Thunder client

https://learn.microsoft.com/en-us/rest/api/eventhub/send-event

Create Azure Data Factory 

Create foreach activity containing web activity and iterate over an array of four items in parallel 

Web activity task takes over 3 to 4 seconds when called from Azure Data Factory Web activity.

Any ideas are welcome.