An approved R$ 100.00 refund, a provider that writes the transaction in 145 ms, and a caller that gives up after 3 seconds without seeing the response. In the first study of the Serverless Under Constraints series, I put Lambda with SQS and Lambda Durable Functions in front of the same ambiguous outcome, in a real AWS account and with an independent oracle: both variants refunded R$ 200.00, and both ended up reporting success.