What redesigning the Pebla mobile money app taught us about building on top of the wallet people already use.
In Rwanda, mobile money runs on USSD codes and SMS confirmations. When we redesigned the Pebla app, the biggest decision was not to fight that, but to build on top of it.
Pebla never holds or moves money. It drives the USSD flow on the user's own MTN MoMo or Airtel Money account, so the PIN is always entered in the network's own prompt. That one choice made the product easier to trust and the architecture simpler.
The SMS is the source of truth. A MoMo confirmation arrives a few seconds after a payment, so refreshing history straight away showed empty or stale rows. Waiting about ten seconds lets the app match the SMS to the pending payment and show the right category.
Dual-SIM phones need care too. Android subscription IDs change when people swap SIMs, so we store the slot together with a network fingerprint. Payments always go out on the SIM the user chose.
Finally, in a financial app, demo data must never look real. We kept sample history behind debug flags during the redesign, so a release build only ever shows the user's own payments.