FREE INTERACTIVE EXAMPLE · NO REAL ORDER OR PAYMENT

The reply vanished.
Did the order?

Make one request. The simulated server saves the order, but its response is lost. Then retry and inspect the result.

1. Ready. Pick an approach and start the experiment.

What the picture leaves out

A real server needs durable state and concurrency control. The included Python/SQLite example demonstrates a local transaction, concurrent duplicate requests and rollback. It makes no external calls.

This browser page is a deterministic illustration. External side effects need provider-supported idempotency or an appropriate durable reconciliation/outbox design; a client-side flag is insufficient.

Technical reference: idempotent requests