Azure Web App PaaS (App Service Plan) with Azure SQL connection inside vNet performance vs outside vNet

Question

I have the following setup:

|--------------------- Internet -------------------------|
  WebApp    <---- non-vNet traffic ---->   Azure SQL Db

• WebApp and Azure SQL Db are in the same data centre.
• There is currently no vNet.
• There's a lot of unavoidable "chatter" going back and forth between Azure SQL Db and WebApp
• The connection string in WebApp is a DNS name for Azure SQL Db (eg mydatabase.database.windows.net ), so it's resolving to an external IP.
• I'm trying to squeeze as much performance out of my app as possible by reducing any network overhead incurred with the "chatter".
• I can't seem to find any docs specifically talking about network performance inside vs outside a vNet on Azure.

1. Is it possible to place a Web App and an Azure SQL Db inside a vNet and if so what caveats are there to this?

2. Will I get better network performance by doing this?

|----------------------- vNet -----------------------------|
  WebApp     <---- vNet traffic ---->     Azure SQL Server

Answer 1

If anything you'll probably get worse latency given the Web App has to do SSTP (point-to-site VPN) to reach that VNET. You'll need to bench both setups but i wouldn't bother.

What i would bother with is adding a caching layer if you don't already have one, in-process or distributed (Redis). Now, that's going to be a dramatic change of events for your fetch latency.

Answer 2

We can definitely deploy the web app inside a VNET using the azure app service environment instead of hosting it in a app service plan.

This is appropriate for application workloads that require:

1. Very high scale.
2. Isolation and secure network access.
3. High memory utilization.

More info here - https://docs.microsoft.com/en-us/azure/app-service/environment/