Updates
Resolved
Amazon have mitigated the issue causing the API errors and therefore the region is functioning as normal again and all Engine Yard infrastructure related operations should now run without issue.
Investigating
Amazon are reporting increased API error rates in the US-East-1 (North Virginia) region. Please hold off from making any infrastructure level changes to environments hosted in this region (instance restart, creation and termination) at this time. If you see any issues with your environments or applications please open a ticket.