The relational database began with Edgar F. Codd's paper "A Relational Model of Data for Large Shared Data Banks" (CACM, 1970), published while he was at IBM Research. More than 50 years later, the overwhelming majority of OLTP workloads still run on top of the relational model. AWS RDS is a service that dramatically reduces the burden of operating that decades-old technology in the cloud. Once you dig deep into what "managed" concretely means, and why Multi-AZ and Read Replicas were built for different purposes, half of the SAA-C03 database questions solve themselves.
Anyone who has installed and run MySQL directly on EC2 knows the drill