Idempotency in APIs: Why Retries Shouldn't Double-Charge Anyone | Clickmasters

Clients send a unique key per operation; the server stores result-by-key and replays the stored response on repeats — same key, same outcome, exactly-once effect atop at-least-once delivery.

Payments, order placement, inventory movements, webhook processing, and every queue consumer — anywhere duplicates cost money or trust.

Skipping the discipline this article describes until an incident, audit, or stalled project forces it — every practice above is cheaper adopted early than retrofitted under pressure.