The parent_call_uuid parameter is available in the Make a Call API. You can use this param and specify the call_uuid of the first leg(parent call) to add the new participant to the same POP as the first participant. It is useful in reducing the delay in bringing a new member to the conference and enhancing the call quality of each conference participant.
You may also use the error_if_parent_not_found parameter to control the behavior of the parent_call_uuid parameter. If this is set to true, then if the parent_call_uuid is not found, the call is not initiated and an error is returned. If set to false, the call will be started by ignoring any error with the parent_call_uuid. The default value is false.
This parameter is honored only for single calls and not for bulk calls. During bulk calls, several participants are likely to enter from different regions. If all participants get added to the same POP as the first leg(parent call), they might experience latency in the call audio.