The bank didn't answer. Did Rohan pay?

transcript

You tap pay. The gateway says nothing for 30 seconds. Did the money leave? Nobody knows.

At the festive peak, payment requests jump nearly 1,000 times. Flipkart's payments VP told Business Standard, as DQIndia reported. Banks weren't built for that. One slows from 2 seconds to 20.

So do you retry? Or call it failed? Retry as new, and you might charge twice. Fail it, and you might take money for nothing. So mark it unknown. Keep the stock held. Ask the gateway.

But here's the catch. Rohan sees pending. He taps pay again. Same idempotency key. Checkout finds the first attempt. No new charge. Just the first one's status.

A reconciler polls the gateway's status. Same key. Success? Confirm the order. The warehouse event commits in the same transaction. Failed? Release the stock hold.

A timeout isn't a failure. It's a question. Ask it until you get an answer.

Full breakdown in the lecture.