[abstractbeliefs]

This is only a useful system if you can trust that failed databases simply disappear.

In failure modes like accidental delete without WHERE clause, or a write that corrupts the validity of the business logic, it's useless, as you can watch the logs to see all your slave machines keenly and unquestioningly repeating the issue.

[Thaxll]

We had that at my previous job, fortunately for some reasons the slave was delayed by like 10min, it saved us from a very very serious problem, especially when you do backups every 6h.