I would consider extremely difficult to setup a reliable system that could listen to webhooks and pause projects.
My main concerns are .. how can you test it and how can you be sure that it is working in all future.
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Are you able to find the twitter post you mentioned?
Here is a link to the twitter post where someone got a 23k bill. In the thread you can find people confused about how this could have happened and why there are not hard limits to prevent situations like this. https://twitter.com/michaelaubry/status/1757539928534315322?...
Here is a comment in the thread from their VP of product explaining how to set hard limits via a web hook. They said they would improve the documentation for it but some people replied saying they shouldn't need a web hook to set usage limits. https://twitter.com/leeerob/status/1757960730865696892?t=mCD...