You can try implementing rate limiting and not exposing your API keys to the public.
You're supposed to drive slow and careful, and not rely on seatbelts and airbags.
Yes, and you should! But not doing so resulting in this seems kind of over-the-top. Basically means an oversight can result in your bankcruptcy?
Google has specifically said that certain API keys like Firebase are not secrets (since people will find them)... though Gemini then ended up changing stuff. https://news.ycombinator.com/item?id=47156925