Since the killOperations command can race over the network, I think a more complete solution is needed. My proposal is a background service that tracks OperationKey values by HostAndPort. Consumer would add an OperationKey with a HostAndPort and an optional deadline. Then the service will include it in a regularly scheduled killOperations after that deadline that it sends to that HostAndPort. Consumers would have to explicitly remove that OperationKey once their operation resolves either naturally or from cancelation.