GCP has a spending limit, but it is by no means transparent[0]
Basically you add a budget to your project, create a pub/sub channel, then make a lambda that subscribes to the channel and turns off billing when it receives an overbudget message to shut everything down.
Or you could integrate it into your project directly to handle this more gracefully.
You can even send a test message, to check that everything does indeed shut down, but the whole process is extremely clunky and error-prone.
Basically you add a budget to your project, create a pub/sub channel, then make a lambda that subscribes to the channel and turns off billing when it receives an overbudget message to shut everything down.
Or you could integrate it into your project directly to handle this more gracefully.
You can even send a test message, to check that everything does indeed shut down, but the whole process is extremely clunky and error-prone.
[0] - https://cloud.google.com/billing/docs/how-to/notify