Okumu Carlos

Usawa (open source) · github.com/nolash/usawa

• Built features for a Python double-entry ledger with a GTK4/Adwaita interface, where entries are cryptographically signed and immutable.
• Refactored the entry model to support arbitrary multi-part entries; added end-to-end tag management, XML export and column sorting.
• Moved wallet encryption from GPG to NaCl SecretBox with argon2 key derivation; supports Unix socket and Valkey storage backends.

[ Python · GTK4/Adwaita · NaCl · argon2 · Valkey · Git ]

Grassroots Economics · Kilifi, Kenya (Remote)

• First USSD engineering hire; designed and experimented with a new USSD menu driver.
• Built and deployed a USSD client for managing custodial wallets and EVM-based Community Asset Vouchers. The live system handles 300+ blockchain transactions a day on the Sarafu Network (dial *384*96#).
• Built an internal menu-traversal driver that automates testing of USSD menu navigation.
• Created service templates, automation scripts and dependency-upgrade tooling to improve developer experience.

[ Go · Docker · PostgreSQL · NATS · Git · EVM ]

KnightFox App Design Ltd · Kingston, Jamaica (Remote)

• Built Stripe and PayPal webhooks on AWS Lambda and SAM for SaaS payments.
• Integrated Zoho CRM with AWS services and implemented real-time payment data capture.
• Built scalable REST APIs with Node.js, Express and serverless functions, reducing development time by 30%.
• Automated payment-data sync with scheduled AWS CDK Lambda functions.
• Wrote Swagger documentation for all endpoints, improving frontend/backend coordination and cutting feature development time by 50%.

[ TypeScript (Node.js) · Go · AWS · MySQL · Git · Bitbucket · Jira ]

SwingWizards · Kenya

• Introduced Protocol Buffers, reducing bandwidth by 40%.
• Designed the frontend communication protocol and worked with backend engineers on integration.
• Designed data models for MongoDB and MySQL.

[ Kotlin (Android) · Go · Protocol Buffers · Git · GitHub ]

Education

BSc Software Engineering · Murang’a University of Technology, Kenya

A school canteen payment and biometric identity system for Kenya. Android app, architecture and roadmap.

[ Android · Kotlin · Jetpack Compose ]

See demo

A Go service that normalizes cTrader, Binance and Alpaca into one WebSocket API: OHLC history, ticks, order books and live streams.

[ Go · WebSockets · Protobuf · cTrader · Binance · Alpaca ]

See demo

Repo: github.com/Carlosokumu/account-connect

Contributor to Go-Vise for the Grassroots Economics Foundation: a constrained-size output virtual machine for USSD-based navigation.

[ Go · USSD ]

Repo: github.com/grassrootseconomics/Go-Vise

A signed, immutable double-entry ledger with a GTK4/Adwaita interface. I refactored the entry model, added tag management, XML export and sorting, and moved wallet encryption from GPG to NaCl with argon2.

[ Python · GTK4/Adwaita · NaCl · argon2 · Valkey ]

Repo: github.com/nolash/usawa