Ravi Sir's Cards › AWS
Idempotent writes
This revision card explains Idempotent writes. It starts from the need that retries without idempotency double-charge or double-ship. It describes use orderId as key + ConditionExpression attribute_not_exists. The how-to section notes putItem with condition , then treat ConditionalCheckFailed as success if same payload. An example on the card is ravi Sir drills idempotency before any SQS lab goes live.
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What this card says
Why do we need it?
Retries without idempotency double-charge or double-ship.
What is it?
Use orderId as key + ConditionExpression attribute_not_exists.
attribute_not_exists
How to do it
PutItem with condition → treat ConditionalCheckFailed as success if same payload.
Example
Ravi Sir drills idempotency before any SQS lab goes live.