Q:

Should an App Service and it's corresponding Web API use the same Application Insights?

I have an architecture where I have a thin ASP.NET Core MVC website that connects to an ASP.NET Web API which handles all of the logic. What is the best practice for setting up Application Insights for the 2 apps? 

Should they use the same AI instance or independent?
How can you track calls from the MVC site to the API so that I can see the corresponding telemetry data for the request?

A:

The previous guideline was to use a different Application Insights resource per app. Now we're transitioning to natively supporting all telemetry reported single instrumentation key.
The end goal is that Application Insights work the same (from UX, alerting, etc.) perspective whether each app instrumented with its own ikey or all apps report telemetry to the same ikey. This future might take time to materialize =) 

