do single AZ AWS RDS instances self heal?
AWS will restart the database if the host has a problem . 

"Automatic Host Replacement
Amazon RDS will automatically replace the compute instance powering your deployment in the event of a hardware failure." 

I don't know if AWS can guarantee in case of hardware failure that you have all transactions. At least having automatic backup you have the status less than 5 min before the failure. 

See https://aws.amazon.com/rds/details/