Amazon 在網頁上說明了在 4/21 美東地區 EBS/RDS 故障的原因：「Summary of the Amazon EC2 and Amazon RDS Service Disruption in the US East Region」。
整篇文章相當長，但整個連鎖反應是起於操作時的人為疏失。而 RDS 因為是基於 EBS 上，所以也跟著大爆炸...
For customers with an attached EBS volume or a running RDS database instance in the affected Availability Zone in the US East Region at the time of the disruption, regardless of whether their resources and application were impacted or not, we are going to provide a 10 day credit equal to 100% of their usage of EBS Volumes, EC2 Instances and RDS database instances that were running in the affected Availability Zone.
另外，AWS 的 SLA 中有要求當未滿 SLA 條件時，必須由使用者提出退款要求，但這次則是例外，符合條件的會主動在下次的帳單上，或是系統的頁面上看到：
These customers will not have to do anything in order to receive this credit, as it will be automatically applied to their next AWS bill. Customers can see whether they qualify for the service credit by logging into their AWS Account Activity page.