Methods, systems, and apparatus, including computer program products, for data structure locking. In one aspect, a proper subset of variables of a set of variables in a data structure are received. An access privilege to modify variables in the data structure to administrator accounts is assigned. A first administrator access request to modify a variable in the proper subset of variables is received, and the access privilege to modify the variable in the proper subset of variables for the first administrator account. A second administrator access request to modify the variable in the proper subset of variables is received, and an access timer that expires after a time period is initiated; the access privilege is disabled for the first administrator account in response to expiration of the access timer; and the access privilege for the second administrator account is enabled in response to expiration of the access timer.