Writing

Essays on African economies, mobile money, crypto rails and the craft of building financial software.

Building

Idempotency is a product decision, not an engineering one

Every retry policy encodes a belief about who absorbs the cost of uncertainty. Usually it's the customer.

19 Aug 2026
2 min
Building

The ledger I wish I'd written first

Three rewrites later, here is the double-entry core I'd start every payments product with.

2 Jul 2026
3 min
Mthunzi
mthunzi.xyz
Colophon. Set in Fraunces and Source Serif 4, with Inter for labels. Charts drawn by hand in SVG. Written and built by Mthunzi Sabali.