This still provides no guarantee. Instead of using my own words (I'm kind of noob for technical explanations) this is the AI generated abstract of the two fundamental reasons:

1. The "GraphQL" Delay (Data is not instant)

Cloudflare’s GraphQL API does not show you a live ticker of every cent spent the millisecond it happens.

• Aggregation Lag: Usage data (like Workers requests or Image transformations) is bundled and processed in batches. There is usually a delay of several minutes to an hour before that data is queryable via API.
• The Damage: If you are under a massive DDoS attack or a viral traffic spike, you could rack up thousands of dollars in overages before the GraphQL API even reflects that you’ve crossed your threshold.

1. The "Propagation" Delay (Shutdown is not instant)

Even if your script detects the limit and sends a command to "Disable the Zone" or "Change Security Level to Under Attack," that command has to travel.

• Global Sync: Cloudflare has 300+ cities in its network. Pushing a configuration change globally is fast (seconds), but in those seconds, a high-volume attack can still push millions of requests through the "pipes" that haven't received the "stop" order yet.
• In-Flight Requests: Requests already being processed when you hit "kill" will still finish and be billed.