Feature
Amazon RDS
Amazon Aurora


Database Engines
MySQL, PostgreSQL, MariaDB, Oracle, SQL Server, Db2
MySQL-compatible and PostgreSQL-compatible engines


Architecture
Traditional DB + EBS storage
Cloud-native distributed storage architecture 


Performance
Standard database performance
Up to 5-6x MySQL and up to 3x PostgreSQL performance in AWS comparisons


Storage Scaling
Depends on engine and configuration
Automatically scales up to 128 TB 


Read Replicas
Up to 5 (varies by engine)
Up to 15 Aurora Replicas


Availability
Multi-AZ deployment
Six copies of data across three Availability Zones


Failover
Minutes in many cases
Typically faster because storage is already shared across replicas 


Cost
Lower
Higher than standard RDS for equivalent workloads


Best For
Small to medium workloads, traditional applications
High-scale, mission-critical, enterprise applications