lesson
A retry should not duplicate the effect
1 · Learn
An idempotent operation has the same intended effect when repeated with the same request identity. This matters when a client retries because it did not receive confirmation, even though the server may already have completed the first request.
A timeout does not prove nothing happened. Use an explicit operation identity or a safe state check rather than blindly creating a second record.
2 · Worked example
If a submission was saved but the response was lost, a retry using the same operation key can return the existing result instead of creating a duplicate.
3 · Your turn
Does a client timeout prove the server did not save the request?
Check your answer
No. The save may have completed before the response was lost.
4 · Apply your learning
Design a test that repeats one fictional submission request and verifies only one submission is created.
Adult guidance and safety
Use an approved sandbox, invented data and test accounts. Do not probe other systems or expose credentials. Retain test evidence and accessibility checks; these teaching models are not a completed practical project or a specified GCSE qualification.
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