depending on your application logic you can get external inconsistencies. like your typical CRUD app might dump the state of an entity in an edit form, then a u

depending on your application logic you can get external inconsistencies. like your typical CRUD app might dump the state of an entity in an edit form, then a user might edit one field, and the whole form is sent to the backend and written over whatever exists there. if you have two different masters then you can get a series of updates where you can't tell if the update is because the user meant to make the change or if it was because the change was incorrectly propagated from the other master. like even if you knew the user read from the other master you can't tell if the user intended the change or not. maybe they saw the value was the value they wanted so they didn't change it. i guess this is a 'bug' because when you do stuff like this you should include some kind of version identifier to catch a concurrent update in the normal case. this scenario is also 'storing stuff outside the DB' kind of similar to the user_id in the cookie getting out of sync.