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Idempotency, retries & failure handlingHardSDE-3
A scheduled job that settles merchant payouts uses a Redis lock with a 30-second TTL so only one instance runs. One day two instances both paid the same merchants. How could that happen, and how do you make it safe?
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PhonePeRazorpayStripeZerodha
Think first
Answer out loud as you would in the room — clarify, give numbers, name the trade-off — then compare with the model answer.
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