It is good and you followed good approach as per M2 standards. It needs some improvement to make it compatible and error-free in a maximum of cases

1. Exception Handling.
`$order = $observer->getEvent()->getOrder(); if( !empty($order) ){ // do code here }`

2. Naming convention. Do use camel-case for variables. `$order_status` should be `$orderStatus`.
3. It is observer so you won't be able to track if that happened or not so do wrap it in try-catch and log accordingly ( do add a check if logs are enabled or not ).