Pulse

The Problem

In Nigeria and across Sub-Saharan Africa, unreliable internet connectivity is a constant reality. Millions of people are locked out of digital financial services every day — not because they don't have a phone, or a bank account — but because a 3G tower went down, or USSD is congested, or the POS machine has no signal.

Existing fintech infrastructure assumes a persistent connection. That assumption fails constantly in emerging markets, and it costs real money for real people.

The Solution

Pulse is a seven-layer offline payment protocol. It allows two parties to execute a financially guaranteed transaction — even with zero internet connectivity — using cryptographic proofs that are reconciled with the network when connectivity is restored.

"The goal was never to build a payment app. The goal was to build the layer that all payment apps in low-connectivity environments should be built on top of."

Architecture Overview

The protocol is structured in seven distinct layers, each responsible for a single concern:

Layer 1 — Identity: Cryptographic key-pair generation per device using secp256k1 (the same curve as Bitcoin).
Layer 2 — Authorization: ECDSA-signed transaction intents. The payer signs an intent; the payee verifies the signature locally without a server.
Layer 3 — Escrow: A deterministic local escrow mechanism that locks sender funds at initiation time, preventing double-spends.
Layer 4 — Transport: Transactions are encoded as QR codes or NFC payloads for zero-connectivity peer-to-peer transfer.
Layer 5 — Queuing: Unreconciled transactions are queued in a local SQLite store with a priority ordering algorithm.
Layer 6 — Reconciliation: When connectivity is restored, queued transactions are batched and submitted to the settlement network in chronological order.
Layer 7 — Dispute: Cryptographic proof chains allow the system to adjudicate disputes without requiring both parties to be online simultaneously.

Engineering Challenge

The hardest part was designing the escrow mechanism to prevent double-spending without access to a shared ledger. The solution was a deterministic nonce system tied to the device clock plus a monotonic counter — making replay attacks computationally infeasible even in offline conditions.

Tech Stack

Node.js React Native PostgreSQL SQLite (offline) ECDSA / secp256k1 QR Transport NFC Supabase (sync)

What I Learned

Building Pulse taught me that the most challenging engineering problems are not about writing clever code — they are about designing systems that remain correct when all your assumptions break down. Network reliability is an assumption. Clock synchronization is an assumption. Even the user having a fully-charged phone is an assumption.

The discipline of adversarial thinking — asking "what if this component is unavailable?" at every layer — is something I now apply to every system I design, regardless of whether it touches payments.