What are two examples of backend calls?

Backend calls in AppDynamics are the interactions that an application component has with external components or services. These can include calls to databases, remote service calls, and interactions between different tiers of an application.

A tier-to-tier request refers to any internal call that happens between different tiers (or nodes) within the same application. For example, a web tier calling an API service tier within the same application ecosystem.

A remote services call is an external call from an application to a service that resides outside of the application's environment, like a call to an external web service, REST API, or a third-party service provider.

References:

AppDynamics documentation on Backend Detection: https://docs.appdynamics.com/21.6/en/application-monitoring/identify-backends