Depends on the region, availability zone, instance type, and time of day. There are always resources if you are flexible. I’ve only ever seen that message when

Depends on the region, availability zone, instance type, and time of day. There are always resources if you are flexible. I’ve only ever seen that message when dealing with spot instances or cutting edge hardware that was in the process of rolling out. I’ve noticed a number of changes over the past couple of years to make it easier to manage mixed pools of compute resources - both spot and on-demand - a good way for AWS to spread load across different instance classes.