As the use of Apache Storm, a distributed real-time computation platform, becomes more widespread in community, scalability of the platform has become a key challenge. Currently, Apache Storm leverages Apache Zookeeper as a message broker for heartbeats and metrics. Using Apache Zookeeper in this manner may have been a good implementation choice at the inception of Apache Storm since it leverages the use of an existing proven open source technology instead of having to implement a proprietary message broker for Storm. However, using Apache Zookeeper in such a fashion has created one of the biggest bottlenecks in scaling Storm. In this paper, we first explore the key scalability issues that this architecture was creating as cluster and workload sizes grow at Yahoo. Next, we discuss in detail a new heartbeat and metrics service, called PaceMaker to address this scalability problem. Finally, we present experimental results to demonstrate that PaceMaker greatly relieves the workload and resource pressure on the ZooKeeper nodes which enables Storm to scale much further.