The project is for custom code to synchronize certain profile data between multiple Drupal websites on different domains.
What a user creates an account on one of the Drupal sites, the process needs to create the same username, email and password on the other sites. The process should use a queue system, either on one of the Drupal domains, or separate, like SQS. A direct entry into one of the domains MySQL might be fine.
We can help with the queue implementation, but you, the developer, should be expert with working with user profiles and with a service or xml or rest interface between the sites.