1. A computer-implemented method, operable in a network comprising multiple service endpoints, said service endpoints running on a plurality of devices, the method operable on a device comprising hardware including memory and at least one processor, the method comprising: (A) defining a first group from an arbitrary set of nodes comprising service instances across the machines of one or more sub-clusters, wherein each node in the first group assumes one or more discrete responsibilities involved in to processing of a request across the first group, wherein, in response to a request made at a node of the first group, one or more nodes in said first group is selected to be responsible for processing of the request, said first group having a first topology; (B) defining a second group from an arbitrary set of nodes comprising service instances across the machines of said one or more sub-clusters, wherein each node in the second group assumes one or more discrete responsibilities involved in processing of a request across the second group, wherein, in response to a request made at a node of the second group, one or more nodes in said second group is selected to be responsible for processing of the request, said second group having a second topology distinct from said first topology; and (C) transitioning request processing from the first group to the second group over a time period based on a responsibility adaptation policy.