Along the same lines as a façade we have the service selector pattern. In this pattern we have a service which fronts a number of other services. Depending on the message which arrives, a different service could be selected to respond to the initial request. This pattern is useful in upgrade scenarios and for experimentation. If you're rolling out a new service and want to ensure that it will function correctly under load then you could make use of the service selector pattern to direct a small portion of your production traffic to the new service while monitoring it closely. Another application might be for directing specific customers or groups of customers to a different service. The distinguishing factor could be anything from directing people who have paid for your service toward faster end points, to directing traffic from certain countries to country-specific services. The service selector pattern can be seen in this illustration: