The IOR codebase needs to be revamped as it has a significant performance problem when dealing with large numbers of namespaces.

Every time a Gateway resource is modified the IOR codebase queries the k8s api server for routes in every configured namespace, consuming a significant amount of time in larger systems (200/500+ namespaces)

https://github.com/maistra/istio/blob/dff17a7a330526ed3ed374b31dc45b7d2ab35636/pilot/pkg/config/kube/ior/route.go#L103-L111

It also has a search based on O(nroutes + ngateways)

https://github.com/maistra/istio/blob/dff17a7a330526ed3ed374b31dc45b7d2ab35636/pilot/pkg/config/kube/ior/route.go#L115-L122

We also need to check if this applies to the 1.1 codebase.