Depending on the Policy specified the shard will return a different output. WaitUntil::FirstSuccess will return the output of the first successful Wire. WaitUntil::SomeSuccess return a sequence with all the output from all the copies of the specified Wire. WaitUntil::FirstSuccess will either stop execution of the current Wire if any of the copies fail or return a sequence with all the output from all the copies of the specified Wire.
Schedules (n) number of copies of the specified Wire, where (n) is the number specified in the Size parameter. The parent Wire will wait until all the scheduled copies have ended and will either return a sequence of values outputs of all the copied Wires or the output of the first Wire that succeeds. Once done, it will continue with its own execution.