When should I choose Provisioned IOPS over Standard RDS storage?
If you have batch-oriented workloads
If you use production online transaction processing (OLTP) workloads.
If you have workloads that are not sensitive to consistent performance
Amazon RDS provisions that IOPS rate and storage for the lifetime of the DB instance or until you change it.
Provisioned IOPS storage is optimized for I/O intensive, online transaction processing (OLTP) workloads that
have consistent performance requirements. Provisioned IOPS helps performance tuning.