Idempotency is one of the most important concepts in backend engineering, especially for SaaS platforms that rely on external APIs, webhooks, and asynchronous processing. Without idempotent operations, systems become unpredictable, hard to debug, and vulnerable to data corruption. What idempotency means in practice An operation is idempotent when executing it multiple times produces the same result as executing it once. This is essential when: external APIs retry requests, webhooks arrive more t