I was looking a lot about the capability for Istio to have programmable routes at the ingress controller as a solid replacement for Kong API Gateway plugins. A simple example would be to have a rule in the Istio Virtual Service that rejects API calls when the user has a license expired in the application that is behind.
That means, the Ingress Controller to be capable enough to query something inside the app to determine the license status, and based on that response, block/allow traffic that is coming from a particular customer (which are being identified by a header)
This is something I do with Kong plugins, but I didn´t find anything similar on Istio.