01 / PaymentsIn progress
ElimuCard
A school canteen payment and biometric identity system for Kenya, with an Android app architecture and roadmap.
Portfolio / Volume 01 / Nairobi, Kenya
Okumu Carlos
Software engineer · Go · TypeScript · Python · Kotlin
I build dependable software for financial data, payments, and USSD. Interested in the systems underneath: clear interfaces, careful data models, and infrastructure that holds up in the real world.
Open to good work
Working principle
Build the useful thing.
Make the data trustworthy.
Leave the system easier to understand.
Built in Nairobi, shipped everywhere →
01 / Selected work
Dispatches
A few systems in progress, in production, and out in the open.
02 / Market dataIn progress
Account-Connect
A Go service that brings eTrader, Binance, and Alpaca into one WebSocket API for OHLC history, ticks, order books, and live streams.
03 / Open sourceContribution
Go-Vise
A constrained-size output virtual machine for USSD-based navigation, contributed to the Grassroots Economics Foundation.
04 / LedgerOpen source
Usawa
A signed, immutable double-entry ledger with a GTK4/Adwaita interface, multi-part entries, XML export, and NaCl-backed wallet encryption.
02 / Where I have worked
Service record
Backend engineering across payments, community finance, and developer tooling.
Jun 2026 — Sep 2026
Software Engineer · Open source
Built features for a Python double-entry ledger; made entries cryptographically signed and immutable; added multi-part entries, XML export, and sorting; moved wallet encryption to NaCl SecretBox with Argon2 key derivation.
Python
GTK4 / Adwaita
NaCl · Argon2 · Valkey
GTK4 / Adwaita
NaCl · Argon2 · Valkey
Aug 2024 — May 2025
Backend Engineer · Grassroots Economics
Designed and deployed a USSD client for custodial wallets and EVM-based community asset vouchers. The live Sarafu Network system handles 300+ blockchain transactions a day.
Go · Docker
PostgreSQL · NATS
USSD · EVM
PostgreSQL · NATS
USSD · EVM
Nov 2022 — Nov 2024
Backend Engineer · Payments
Built Stripe and PayPal webhook integrations, connected Zoho CRM with AWS services, and developed serverless REST APIs and scheduled payment-data syncs.
TypeScript · Node.js
AWS Lambda · CDK
Express · MySQL
AWS Lambda · CDK
Express · MySQL
Jul 2020 — Feb 2022
Backend Engineer · Swings
Introduced Protocol Buffers to reduce bandwidth, designed service communication and data models, and supported frontend/backend integration.
Kotlin · Go
Protocol Buffers
MongoDB · MySQL
Protocol Buffers
MongoDB · MySQL
Education
BSc Software Engineering
Murang'a University of Technology
Kenya
03 / Tools of the trade
The kit
A practical toolkit, shaped by the work rather than the other way around.
Languages
Go · TypeScript · JavaScript · Kotlin · Python · SQL · Bash
Backend & tools
Node.js · Express · REST · WebSockets · AWS (Lambda, SAM, CDK) · NATS · Protocol Buffers · Docker · Git · Swagger
Domains
Financial market data · Algorithmic trading · Real-time data · USSD · Stripe and PayPal payments · EVM and blockchain · Double-entry accounting · Applied cryptography
Databases
PostgreSQL · MySQL · MongoDB · Valkey
Always reading the logs first.
04 / Contact
Send a dispatch.
Have a project, a role, or a question? I read everything.