I believe AWS can create spot autoscaling groups which include a minimum baseline traditional instances plus a floating level of spot instances. This seems to be a nice compromise.

Just spin up regular VMs if you can't get spot instances when you need them.

Lack of spot VM means that all spare capacity has been taken up by the regular VMs, meaning that it spots are gone, so are regular ones.

Having worked on infrastructure deployed this way, I can say this oversimplifies a bit. There's virtually never no spot capacity at all, there's no capacity at a given bid price, for a given instance type, in a given region. You can start to scale up on-demand infrastructure using spot price as a signal, before there's literally none left, and you can also run on clusters of heterogeneous instances, and change your instance type mix when one instance type's price goes up. In the worst case you can fail out of a particular region whose spot prices have gotten too high. Lots of options.

No shade, but this is a very AWS specific view of cloud. Every cloud has a different resource allocation philosophy, not all the assumptions are the same.

Yeah, GCP spot instances don't vary in price like AWS ("The price adjustments will occur at most once a month").

There is no longer bidding for spot prices on AWS. They moved to model where pay the fixed spot price which isn't based on capacity.

https://aws.amazon.com/blogs/compute/new-amazon-ec2-spot-pri...

Interesting! I think it still updates more than once a month, but that is a significant change that I wasn't aware of, thank you.

Maybe that's true but we haven't seen this happen in practice. Maybe we're just incredibly lucky but we're able to get on-demand instances to recover after spot termination.

No guarantee but still very likely there are instances available.

Spot is excess capacity. If there's zero excess capacity, that means there's (probably) also no on-demand capacity as well.

If you are not being given any excess capacity, that doesn't mean there is no excess capacity. You are just not one of the lucky few, whose numbers are shrinking.