Writing
- Money is an integerEvery money bug I have fixed in ten years came back to one of three mistakes. All three go away when you store sen, not ringgit.
- Idempotency is a product featureWhen a payment times out, the customer taps again. Whether that charges them twice is not a backend detail. It is the product.
- The 640 millisecond checkoutHow we took the slowest step of a grocery checkout from 2.8 seconds to 640 ms, mostly by deleting things.