Ravi Sir's Cards › AWS
Idempotent receipts
What is a VPC: your own private network inside one AWS Region, example ThreeTierVpc 10.0.0.0/16.
Read card text
What this card says
Why do we need it?
S3 can retry the same ObjectCreated event. Double email confuses users.
What is it?
Idempotent = doing the same work twice is safe. Key the DynamoDB receipt by object versionId or etag; skip if already sent.
How to do it
PutItem with condition attribute_not_exists(receiptId) or GetItem first; only then SendEmail.
attribute_not_exists
Example
Two deliveries of the same event → one email, one DynamoDB row.