We have a machine where with a heavy cpu load on myqsl process on Server 1.
Our webapp on server 2 suddenly seemed to bypass rights logic and expose some data as if no check were done on the db side.
Can an app miss some SQL queries because the DB server is under heavy load ?
Can MySQL loose consistency ?
Probably not. More likely, your application detected an error with the database(maybe a timeout), but is not handling the error properly. I would check the application exception handling logic carefully.