99% automatic PostgreSQL/MySQL replication?

Question

MySQL

I saw that there are 2 types of replication: Master-Master and Master-Slave.
And here and there, as I understand it, you need the constant presence of a person.
For example.
In the Master-Slave, the Master lay down and the Slave becomes the Master, but he himself will not understand that it is time to become the Master?
And when the old Master gets up, he will not understand that he was lying and will not guess to become a Slave.

How to make everything as automated as possible?

Answer 1

The master did not go down, but the network between the master and the replica was broken. The replica has become a master.
Your actions? You have two masters, each of course believes that he has the correct data.
It's called split brain. It is not automatically repaired in principle.
In other words - why do you need this abundance of headaches?