I understand that database backup is a full copy of the database and serves as the last resort in a disaster where data is lost -- recovering data.
In the case of multi-AZ standby db deployment, we already have multiple copies of the data, thus it's unlikely that all of them will be destroyed. With that in mind, do we still need database backup in this case? Or we can just use the other standby instances as backup?
Note that I'm not talking about snapshot here. I do understand we still need to take snapshots to revert changes in case of an accidental change or human error.
Multi-AZ is backup only within same region. It does not protect you from data loss caused by entire region outage or destruction.
For mission critical databases you can either create read replica in a different region for live backups, or a cheaper solution is to copy db snapshots to different region on periodic basis.