Which approach should an Integration Architect recommend for displaying data from an external system inside of Salesforce without enabling Lightning Experience?

The recommended approach involves using an iFrame to embed a custom .Net application. This solution allows for the display of data from an external system directly within Salesforce without requiring Lightning Experience. By utilizing an iFrame, the external application can be rendered within the Salesforce interface, effectively presenting the necessary data to users in real-time.

This method is beneficial as it can seamlessly integrate data without needing to migrate or duplicate the data into Salesforce. As long as the external application can handle Cross-Origin Resource Sharing (CORS) appropriately, it can display content without significant security concerns. Moreover, this approach benefits from the existing infrastructure of the .Net application and capitalizes on its features and functionality without redesigning it for Salesforce.

While other approaches like utilizing a custom visualforce page or a middleware orchestration also serve to integrate external data, they may involve more complexity or require additional tools and maintenance. For example, a visualforce page can be effective, but it typically involves more intricate coding to handle data retrieval and display, which could complicate the solution. On the other hand, middleware orchestration generally entails moving data into Salesforce, which may not be necessary if the goal is simply to display external data. Thus, embedding the iFrame strikes the right balance between simplicity and