One of the most common issues we face is creating a REST API for our client which is hosted on a brand new domain while the client application is being hosted on the clients old domain. Specifically when client demands that we carry both the system parallel for couple of months until he/she has confidence on the upgraded API's. In our own company we found this issue when launching a brand new domain for a new application. Unfortunately the new application hosted on the new domain talks to our old REST API hosted on our company domain. Problem!