Auto top-up
Usage & billing can add credit from a saved card when your balance falls below a line you pick, up to a monthly most you set. Each automatic top-up earns 5% more as credit, and while it is on your account runs 200 sandboxes at once instead of 100. A declined charge turns it off and never stops a running sandbox. Also runtime billing auto-top-up, the SDKs and /v1/billing/auto-top-up. See auto top-up.