A. Self-built database support quick deployment and elastic scaling.

B. RDS requires no O&M while self-built database require a dedicated DBA for maintenance, which results in high HR costs.

C. RDS features a high availability of 99 95% while self-built databases require you to implement data protection primary-standby replication, and RAID all by yourself.

D. RDS provides automatic backup while self-built databases require you to prepare storage space for backup copies and regularly verify that these copies can be restored.