(define (update-db db key #!key user password comment)
  (let ((entry (or (alist-ref key db equal?) (make-list 3 ""))))
    (alist-update key 
                  (match-let (((u p c) entry))
                             (list
                              (or user u)
                              (or password p)
                              (or comment c)))
                  db
                  equal?)))