Messaging & event-driven designHardSDE-3

You key payment events by merchant_id. One large merchant produces 40% of all traffic, so one partition is always lagging while others are idle. What do you do?

Asked at

PaytmPhonePeRazorpayStripe

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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