1. A method of processing a client-initiated request, performed by a respective server system having one or more processors and memory storing one or more programs that when executed by the one or more processors cause the respective server system to perform the method, the method comprising: receiving, from a client system, a respective request including server identifiers for one or more other server systems distinct from the respective server system; after receiving the respective request, determining whether at least a predefined number of the other server systems have a predefined task-processing status for the respective request; and in accordance with a determination, prior to processing the respective request, that at least the predefined number of the other server systems have the predefined task-processing status for the respective request, performing a corresponding task-scheduling action that overrides a default task-scheduling policy as applied to the respective request; and in accordance with a determination to perform a respective task-processing operation for the respective request at the respective server system: sending a processing-status message to one or more of the other server systems indicating that the respective server system has undertaken performance of the respective task-processing operation for the respective request; and performing the respective task-processing operation.