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What the client observed
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0.000s client POST /payments amount=4200 0.014s server handler entered 1.870s server committed charge_01H8Z 2.000s client read timeout — no response bytes 2.001s client reported to caller: FAILED 2.410s server 200 OK written to a closed socket
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A timeout tells you one thing only: no response arrived in time. It says nothing whatsoever about whether the operation ran.
Why the obvious fix makes it worse
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- Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis
- Nisi ut aliquid ex ea commodi consequatur, quis autem vel eum
- Iure reprehenderit qui in ea voluptate velit esse quam nihil molestiae
Reproducing it locally
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def post_payment(request): charge = ledger.commit(request.body) # side effect happens here time.sleep(SLOW_RESPONSE) # the response is what's late return Response(200, {"charge": charge.id})
The money moved. Your logs, your client and your customer all believe it did not.
Where idempotency actually belongs
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What to take away
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Placeholder endnote — this is where the reproduction steps, the environment details and any corrections would live, so a reader can run the experiment themselves and disagree with the conclusion.
Reading it is not the same as causing it.
Module 04 hands you the server, the impatient client and the ledger. You make the timeout happen, retry it, watch the duplicate charge land, then move the identity decision to the side that owns the state — and prove it holds.