> The real answer to all this is to use a provider that supports idempotency keys. Then when you can retry the action repeatedly without it actually happening again. My favorite article on this subject: https://brandur.org/idempotency-keys

Turtles all the way down?

Let's say you are the provider that must support idempotency keys? How should it be done?

Offer 99.something% guaranteed exactly-once-delivery. Compete on number of nines. Charge appropriately.