available

Zacharia Kamau Ndung'u

~/Full-Stack Software Engineer | Fintech & Payments Infrastructure

I design and build resilient payment infrastructure, distributed systems, and developer-friendly products that remain correct under scale.

view work →get in touch
◈ Nairobi, Kenya·2026 — open to collaborations
Zacharia — ~/portfolio
Zacharia@dev:~$
scroll ↓
$cat about.md

I'm a Full-Stack Software Engineer specializing in fintech, payment systems, and distributed backend architecture. Over the last three years, I've built and maintained critical financial infrastructure that processes transactions, manages ledgers, and powers business operations at scale.

My work spans the entire stack—from designing database schemas and backend services in Spring Boot and NestJS to building operational dashboards in React and Next.js. I focus heavily on reliability, security, and system correctness, especially in environments where financial data and transaction integrity are non-negotiable.

I've worked extensively with M-Pesa integrations, ledger systems, API gateways, distributed locking, asynchronous messaging, and cloud-native deployments across GCP and AWS. Outside engineering, I write about software architecture, payment systems, and my journey in technology.

3+
years building production systems
10+
microservices delivered
Millions
in transactions processed
$ls ~/stack
▸ languages/
  • — TypeScript
  • — Java
  • — Python
  • — SQL
▸ frontend/
  • — React
  • — Next.js
  • — TanStack Table
  • — Tailwind
▸ backend/
  • — NestJS
  • — Spring Boot
  • — Flask
  • — PostgreSQL
  • — Redis
  • — RabbitMQ
▸ infra/
  • — GCP
  • — AWS
  • — Docker
  • — GitHub Actions
  • — Keycloak
  • — APISIX
$ls -la ~/projects

Selected work

03

SpaceAndOccupy

Multi-tenant SaaS platform

Cloud-native property management platform serving landlords, property managers, and tenants.

FlaskReactCeleryRabbitMQGCP
Full-Stack Engineer2023↘

Architected a multi-tenant SaaS platform for rental and property management. Designed asynchronous task processing with Celery and RabbitMQ, deployed services on GCP Cloud Run, and resolved production reliability challenges involving worker health checks, networking, and messaging infrastructure.

open case study →
04

Invoicing & Quotation Service

Automated invoice-to-payment workflow

Event-driven invoicing platform with PDF generation and integrated M-Pesa payment collection.

Spring BootRabbitMQOpenHTMLtoPDFM-Pesa
Backend Engineer2023↘

Developed a standalone invoicing microservice supporting quotation generation, PDF exports, payment collection, and event publishing. Designed around an event-driven architecture to maintain loose coupling between financial and operational services.

open case study →
$git log --oneline experience

Full-Stack Software Engineer

@ KiotaPay
Dec 2024 — present● now
  • › Own and maintain the payment gateway and ledger microservices, which process all payouts across the platform.
  • › Built a Redis-based distributed lock service ensuring idempotent transaction processing even during pod scaling or redeployments.
  • › Implemented secure authentication with JWT via Keycloak and APISIX for API traffic routing and token validation.
  • › Developed the Roles & Permissions microservice (Spring Boot) used for user management across all internal apps.
  • › Led NestJS backend work including server-side pagination, Hakikisha phone lookup integration, and TanStack Table frontend features.
  • › Built a nightly ledger regeneration batch system with Redis distributed locking, rolling over a 4-night cycle.

Software Engineer

@ Kelhel
Oct 2024 — Dec 2024
  • › Designed and developed a Point of Sale platform for pharmaceutical operations covering sales, inventory management, and customer records.
  • › Integrated M-Pesa Daraja payment processing to support secure and reliable mobile transactions.
  • › Built scalable APIs and backend services using Nest.js and PostgreSQL.
  • › Developed responsive frontend experiences with Next.js, Redux Toolkit, and ShadCN UI.
  • › Implemented reporting and inventory tracking capabilities that improved operational efficiency and stock visibility.

Front-End Software Engineer Intern

@ Dowell Research UK Limited
Jun 2023 — Oct 2023
  • › Developed responsive web applications focused on usability, accessibility, and performance.
  • › Built custom WordPress plugins that improved user experience and platform accessibility.
  • › Collaborated with remote teams to deliver client-facing features across multiple projects.

Technical Content Writer

@ Upwork
Jan 2021 — June 2023
  • › Produced technical content covering software engineering, payment systems, system architecture, and web development.
  • › Researched and translated complex technical concepts into clear and practical learning materials.
  • › Worked with international clients across fintech, SaaS, and technology sectors.
$cat ~/writing/*.md
paymentsIdempotency in Payment Gateways: Why Your Money Moves Exactly Once2026 · 7 min→
LearningFrom Delivering Cakes to Writing Code: My Journey into Software Engineering (Part 1)2025 · 4 min→
JavascriptHow Javascript Works Behind the Scene2023 · 3 min→
JavascriptConfiguring Tailwind CSS in a React JS Project2023 · 4 min→
$./contact.sh

Let's build something.

Open to senior/staff fullstack roles, contract work, and interesting open-source collaborations. Fastest way to reach me is email.

ndunguzachary24@gmail.com →
githubgithub.com/Zackius↗linkedinlinkedin.com/in/zachariandungu↗emailndunguzachary24@gmail.com↗mediummedium.com/@ndunguzachary↗