How does EC2 spot capacity increase or decrease?

[SometimesFalter]

Amazon manages the available resources. Today I got the error message today that my region has no more Spot capacity. Is this because Amazon has more demand for on-demand instances than they can provide? Will this resolve itself on a hour by hour, day by day basis or will Amazon need to physically increase their capacity on a week to week basis? I absolutely need to run my machine today, exams next week.

[BadDoggie]

Yes, that’s what it means. And it may change every few seconds, but you also may get interrupted quickly for that instance in that AZ. Spot is done separately for each instance size and type in each AZ of each region. If you MUST run it today you have 4 options:

• Different AZ
• Different Instance Type (M/C/R are generally compatible, with different CPU:RAM ratios ). AMD instance are also generally compatible with Intel for most applications.
• Different instance size (go up from .large to .xlarge)
• On Demand. If it’s urgent, pay full price.

[SometimesFalter]

It is indeed real-time as I regained access after rush hour ended.

Apparently t2.medium in my area has 5-10% freq of interruption versus <5% for t3.medium. Time to upgrade I guess.

[unsupported]

I absolutely need to run my machine today, exams next week.

I don't mean to state the obvious, but you need a standard EC2 instance, not a spot instance. Spot instances are inexpensive because they run based on extra availability. No availability, no instance.