alt Hacker News> Trading platforms can guarantee a maximum slippage on stops
Yeah no, physically impossible. If nobody is selling at that price, there is no guarantee your sell stop will execute near that price. They can sweep the market, find the best seller price and execute.
There might be a costly way to do it with microservices as I indicated, but your example easily falls apart.
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If they are a market maker, they can buy/sell at or near your stop. It might be a bad idea for them, but if they have a guarantee, this is how they will do it. Or, it will be like the Amazon guarantee (refunding free shipping on your late order).
Not impossible to do: they can hedge and/or absorb the cost, hence the premium. They usually also specify a (fairly large) minimum distance for such stops.
They can take the other side of your other themselves, lose money sometimes, but make it up in the premium they charged you in the first place (or in the old days, from your other trading fees or your monthly subscription payment).
Cloud providers would be taking way less risk interacting with their own services than a broker does interacting with the market. Perhaps they would be more at risk from bad actors, but it shouldn't be significant: they could reserve this behaviour for people who have already spent, say, $100 with them so you can't abuse it at scale.