Key person dependency creates single points of failure when specific employees possess irreplaceable expertise, client relationships, technical skills, or institutional knowledge. Risk materializes through unexpected departure, incapacitation, or unavailability during critical periods. Mitigation strategies include succession planning, knowledge documentation, cross-training, retention incentives, and key person insurance. Organizations assess this risk through competency mapping and business impact analysis. A software startup realized their sole DevOps engineer represented critical dependency; his hospitalization caused a three-week deployment freeze, prompting immediate hiring of backup talent and documentation of infrastructure procedures.