SSO is for users, and credential lifetime is usually on the order of months. Vault is for service to service authentication keys/secrets, which are traditionall

SSO is for users, and credential lifetime is usually on the order of months. Vault is for service to service authentication keys/secrets, which are traditionally static because changing them is a complex process (you need to make sure you don't break services by forgetting them or updating credentials in the wrong order). Vault automates credential creation and rotation.