Use cases are really needed for novices and for those who do not practice these kind of solutions in production. That's why you'll see schema with explanations of what could happen in production. Now, let's discuss outages and how to resolve them.
In a replication mode, you can encounter errors if you do not respect what has been established. A common mistake is for the privileges to be configured on a slave node and not the master.
Here is a scenario with a database as an example:
A junior database administrator connects to the slave server as someone asked for a new database and creates a database crap. The database is ...