Pipeline between two apps

 This seems to be pretty straightforward with a Pipeline.

The pipeline would trigger when a record is changed or added in app one. 

The next step would be to search app to filtering where the ID is equal to the ID from the trigger record.

Then you would do a for each loop to update all of the records that match.  I'm not sure if you also want to do a name match in addition to the ID but that would be part of the search criteria.