Idempotency in Distributed Systems — Why Your Retry Just Charged the Customer Twice
Here is a bug that has cost real companies real money: a customer taps “Pay ₹50…
Tag
payments
14 posts
Payments Engineering in India — From UPI to Ledgers
Every app in India takes payments now. Food delivery, ed-tech, D2C brands, SaaS…
Capstone: Designing Payments for a Real D2C Product
We’ve covered a lot over eleven lessons. In this last one, let’s design the…
Fraud, Security and Compliance for Payment Systems
One Sunday morning, an online grocery company’s monitoring showed something…
Settlement and Reconciliation — Making Three Records Agree
On the 3rd of every month, the finance team at a D2C company I worked with would…
Refunds, Chargebacks and Disputes
A support lead at an online electronics store once told me, “Refunds are where…
Designing a Double-Entry Ledger — Every Paisa Accounted For
A wallet startup I advised had a simple design. The table had a column. Top-up…
The Payment State Machine — Modelling Status and Handling Pending
On a payments team I worked with, the table had a column called . Over three…
Integrating a Payment Gateway the Right Way
When I review payment integrations, I usually find the same three or four…
Idempotency, Retries and Webhooks — Never Charge Twice
Here’s a bug I helped debug at a mid-sized ed-tech company. Some students were…
Card Payments Explained — Auth, Capture, OTP and Tokenisation
A friend runs a small online furniture store in Jaipur. Average order around ₹2…
UPI for Engineers — Intent, QR, Pending and Reversals
One evening during an IPL final, our support queue suddenly had 300 tickets with…
How Money Moves in India — Players, Rails and Settlement
In my first job at a Bengaluru startup, I was asked to “add Razorpay” to our…
Timeouts, Retries and Idempotency
Here’s a bug I’ve seen in some form at three different companies. A cashback…