The circuitbreaker everyone would want is probably: "Drop all compute with its ephemeral storage, when the cost of every resource already used and the projected

The circuitbreaker everyone would want is probably: "Drop all compute with its ephemeral storage, when the cost of every resource already used and the projected cost of my stable storage (EBS+S3+Glacier+Aurora+Whatnot) is greater than my preset $MONTHLY_MAXIMUM. That means any data getting lost as a result of that limit is data that they weren't guaranteeing in the first place. You might not be able to actually read your EBS volumes, S3 buckets or Aurora tables without increasing the spending limit or otherwise committing more funds, but it won't go away that second, and you would have enough time to fix it (worst case - wait until next month; you did budget that already). Alternatively: assign each resource to a pool, and monthly spending limits to each pool. Give your EBS/S3 $1000/month, and your R&D-pet-project-that-may-accidentally-spawn-a-billion-machines $50/month.