$ ls ~/blog

// notes on backend, systems, performance, and AI.

Making Payments Bulletproof: Idempotency, Race Conditions, and Never Charging Twice

Aug 5, 2026

A payment looks like one event, it's actually three racing signals fighting to confirm the same money. Here's how we closed the concurrency gaps behind "charged twice" and "paid but no order" bugs in a production checkout flow.

#Payments#Distributed Systems#Backend#Idempotency#Razorpay#Node.js