When EBS failed in US-East a year or two ago, my RDS instance did not remain available and did not automatically fail over to its replica, despite my paying for

When EBS failed in US-East a year or two ago, my RDS instance did not remain available and did not automatically fail over to its replica, despite my paying for these benefits. Even when it was working correctly, the RDS instances had low capacity compared to physical servers, and there were often spikes of significant latency that would lead to overloaded web servers as DB queries backed up unanswered.