Assign an employee to a team, meaning create a membership. For companies with nested teams, two extra semantics apply. Propagation: memberships are inherited upwards, so after adding an employee to a sub-team, inherited membership rows for its ancestor teams are materialized asynchronously — rows you did not create will appear in later reads. Reuse: if the employee already has a membership row on that team (typically an inherited one), no new row is created — the employee becomes a direct member of the team, the lead flag is applied, and the existing row (with its existing id) is returned instead of a new resource. The response is still 201 when an existing row is reused, so compare the returned id against what you already hold to tell the two cases apart.