Splitting staff data across a scheduler, a clock, an HR tracker, and a contract system means every change is N reconciliations: the new hire goes in the HR tracker, gets added to the scheduler, gets a punch-clock profile created, gets a contract emailed. Each system has its own identity model; payroll month-end is a manual cross-check; and when someone leaves, removing them is N delete operations across N systems with N chances to leave a stale account active.
SP Photo Station starts from the working assumption that an operator shouldn't be the integrator. One staff_members row carries the person through hiring, onboarding, scheduling, shift claims, punches, ratings, badges, and contract signing. Every event references that one record. Reliability grades aggregate across all four signals. Audit trail is single-tenant and queryable from one place.