Idempotency का अर्थ है कि एक operation एक बार या कई बार किए जाने पर समान परिणाम उत्पन्न करता है। यह distributed सिस्टम में महत्वपूर्ण है क्योंकि retries और duplicate messages अपरिहार्य हैं — idempotent operations इन्हें सुरक्षित बनाते हैं।
Idempotency क्या है
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An operation is IDEMPOTENT if doing it MULTIPLE times has the SAME effect as doing it ONCE:
→ "set balance to 100" → idempotent (same result however many times)
→ "add 100 to balance" → NOT idempotent (each call changes it → wrong if duplicated!)
→ in HTTP: GET, PUT, DELETE are idempotent; POST typically is NOT
यह distributed सिस्टम में क्यों मायने रखती है
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Retries and duplicates are INEVITABLE in distributed systems:
→ a request times out → the client RETRIES → but the original may have succeeded →
the operation runs TWICE (e.g. a payment charged twice! an order placed twice!)
→ message queues often guarantee AT-LEAST-ONCE delivery → duplicates happen
→ network issues, failures → operations get retried
→ if operations are IDEMPOTENT, duplicates/retries are SAFE (no harm from repeating)
→ this is essential for correctness and safe retries.