Business problem: A small software firm wants to break into a new market with a mobile app for tracking customer service requests at Department of Motor Vehicles (DMV) service locations. The app will allow users to take a number with their mobile device as they pass into a geofence representing the service area. This will allow customers to immediately move to the next available window or to take a seat and wait comfortably for an associate to assist them. One primary business requirement states that service will be delivered to customers on a first-come, first-served basis. In addition to the business requirements, the team wants to implement the core functionality with a generic design so that they can expand to new markets without the need to modify the underlying business logic.

The developer in charge of creating the core functionality decides that the class that keeps track of each customer's position in line should be bundled with the web service. This...