[MichaelZuo]

> Basically, one of the problems was customers who just set the spot price to 10x of the nominal price and leave the bids unattended. This was usually fine, when the price was 0.2x of the nominal price. But sometimes EC2 instance capacity crunches happened, and these high bids actually started competing with each other. As a result, customers could easily get 100 _times_ higher bill than they expected.

Thanks for sharing, though I'm confused about this part. It seems like expected behaviour?

Any possible spot/auction system I can think of would have the inherent possibility of a sudden surge in pricing.

[cyberax]

Sure. It was the correct behavior, inherent to any market system. Like Texas electrical spot market: https://theconversation.com/whats-behind-15-000-electricity-...

But it turns out that this is not a customer-friendly behavior. So AWS decided to remove the bidding out of the equation, and instead terminate instances based on a complicated scoring system.

The idea is that it's easier to deal with the missing compute capacity, which you notice right away, rather than be blindsided with a 100x bill at the end of the month.