Shortest path query processing on dynamic road networks is a fundamental component for real-time navigation systems. In the face of an enormous volume of customer demand from Uber and similar apps, it is desirable to study distributed shortest path query processing that can be deployed on elastic and fault-tolerant cloud platforms. In this paper, we combine the merits of distributed streaming computing systems and lightweight indexing to build an efficient shortest path query processing engine on top of Yahoo S4. We propose two types of asynchronous communication algorithms for early termination. One is first-in-first-out message propagation with certain optimizations, and the other is prioritized message propagation with the help of navigational intelligence. Extensive experiments were conducted on large-scale real road networks, and the results show that the query efficiency of our methods can meet the real-time requirement and is superior to Pregel and Pregel+. The source code of our system is publicly available at https://github.com/yangdingyu/cands.