Techniques disclosed herein provide an approach for creating and managing aggregation service hierarchies, such as hierarchies used in distributed scheduling services and heartbeat services. In one embodiment, management nodes accept host computer registration events and add host computers to a hierarchy used as the aggregation mechanism in an aggregation service. The management nodes each manage a portion of the hierarchy and configure registered hosts to take the roles of leaf, branch, and root nodes in the hierarchy. Further, the management nodes dynamically mutate the hierarchy by reassigning host roles, in response to host additions and failures, thereby maximizing fault tolerance/high availability and efficiency.