I've noticed a cost difference between the GCP billing and the Sandbox in CMP which would eventually affect the services running there when the default $100 limit is reached. The cost difference is due to using AlloyDB in the sandbox, which is currently in beta and is free of charge for fair use in any GCP project. Google solves the charging by applying a discount in the GCP project. However this discount is not reflected in the DoIT sandbox overview.
Currently credits are not considered as part of budgets in DoIT sandbox costs and this is by design. The reason for this is that if you would for example get free promotional credits from Google or you've got Committed Use Discounts (CUDs) these could be assigned to any project. The allocation of these credits will be at Google's discretion, with the same usage some projects might benefit from more credits than others, they are not allocated in a way we could predict.
I can understand the reasoning. However I wonder whether you want to revisit this decision. In the current case the promotional credits apply for any (fair) usage of AlloyDB in all projects. This might be again the case in the future when Google introduces a new feature as beta and applies no charge (i.e. discounts) for any (fair) use in any project. I wonder whether such "global" or "for all" promotional credits could be somehow distinguished from the other CUDs or promotional credits which are one-time or can be used only in some projects. This would definitely help trying out new features from Google in a sandbox, which to my understanding is one of the core use cases for a sandbox.
See support ticket https://app.doit-intl.com/customers/PREQ32F3HuqJs7UAzNy8/support/tickets/77077 for further details.
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