card on file
card on file
Definition
"Card on file" means a credit or debit card stored on a service account so the provider can charge it automatically. The family's non-negotiable rule is to never put a card on file with any pay-as-you-go provider.
Expanded
The reasoning is failure-mode asymmetry. The failure mode of "card not on file" is "service stops at quota" — acceptable. The failure mode of "card on file" is "card gets charged thousands when quota is exceeded by a bug or attacker" — unacceptable. Documented 2025-2026 incidents include simmer.io ~$98K, Tamara ~$70K, a €54K Gemini key.
This is why the family stays on Firebase Spark forever (never Blaze), Cloudflare free (never paid plans), and why every service in the catalog is pinned to its free tier with explicit "we never hit this because…" justifications.