The product I'm working on right now is taking this approach. We're upgrading a legacy system. In doing so, we're writing a REST API and the components that we

The product I'm working on right now is taking this approach. We're upgrading a legacy system. In doing so, we're writing a REST API and the components that we replace are all built to use the API rather than the old legacy data layer. The goal to to completely replace the application with an API and several UIs, including a full web UI, a mobile UI, and also 'embeddable' UIs. The API also serves as an integration point for other products in our suite. That allows us to scrape a dozen different SOAP services that are targeted to specific integrations and have those other products all utilize a single API that can do anything that the full product can do. I'm really happy with this architecture.