In highly dynamic IoT environments such as Vehicle-to-Everything (V2X), discovering and providing Internet of Things (IoT) services to users is a challenging problem because the environments alter too quickly and unpredictably. For a fast and effective service discovery in a highly dynamic environment, we propose a cached service registry on mobile entities along with new metrics for evaluating the effectiveness of service discoveries. We conducted an experiment on a simulated V2X environment, and showed that both the rate of finding accessible services and the utilization of services can be improved comparing to the traditional service discovery method.