Building Scalable
Mobile & Backend
Systems
Full Stack Engineer specializing in Flutter mobile apps, backend REST APIs, and enterprise system modernization. Currently at Pensoft Systems Limited.
Engineering systems that scale and endure
I'm Nicholas Otieno, a Full Stack Software Engineer with over 8 years of experience building production-grade mobile applications and backend systems. I work across the full delivery stack — from designing clean mobile UX in Flutter to architecting REST APIs and modernizing legacy enterprise platforms.
At Pensoft Systems Limited, I lead efforts to transform monolithic banking and insurance platforms into modular, API-first architectures. I bridge the gap between legacy .NET systems and modern mobile clients, integrating OAuth2, JWT-based auth, biometrics, and AI-compatible tooling where it adds real value.
I care about building systems that are maintainable, secure, and fast — not just systems that ship.
Where I've worked
Software Engineer
Pensoft Systems Limited- Build and maintain Flutter mobile applications for insurance and fintech platforms, serving enterprise clients across East Africa.
- Design and implement REST APIs consumed by mobile frontends, enforcing JWT + OAuth2 authentication and role-based access control.
- Modernize legacy banking and insurance systems written in .NET, migrating monolithic services into modular, API-driven architectures.
- Integrate systems with AI tooling using MCP-compatible architectures, enabling context-aware automation within enterprise workflows.
- Implement mobile security patterns: biometric authentication, certificate pinning, and secure local storage on iOS and Android.
- Lead CI/CD pipeline setup for mobile app delivery to both App Store and Google Play.
Freelance Mobile Engineer
Independent Clients- Delivered 10+ production cross-platform apps on Play Store and App Store across fintech, real estate, beauty, and gaming domains.
- Led end-to-end mobile delivery: requirements, architecture, implementation, deployment, and post-launch support.
- Built SternPay, FineFoods, Finelooks, Housinn, and Mini-Sports — all live in production.
University of Nairobi
BSc. Computer Science
2014 – 2018Google Africa Developer Scholarship
Flutter Development Track
2020 – 2021Udacity
Android Developer Nanodegree
2019 – 2020Things I've built
A selection of production systems — from fintech mobile apps to enterprise modernization work.
Insurance Mobile Platform
Problem: A major insurance provider ran on a monolithic .NET system with no mobile interface, requiring manual agent workflows and paper-based processes.
Solution: Designed and built a Flutter mobile application backed by newly architected REST APIs, enabling digital policy management, claims tracking, and agent dashboards.
- Clean Architecture with domain-driven layers for testability
- OAuth2 + JWT with biometric re-authentication
- .NET backend decomposed into versioned API modules
- Offline-first data sync for low-connectivity field agents
SternPay — Fintech App
Problem: Users needed a fast, secure way to manage digital payments and transfers across multiple currencies.
Solution: Cross-platform fintech application with real-time transaction processing, KYC verification flow, and encrypted local storage.
Mini Sports — Game Platform
Problem: Client wanted a multi-game mobile platform with real-time leaderboards and cross-device state persistence.
Solution: Built a Flutter game app with modular mini-game architecture, Firebase Firestore for real-time sync, and custom game-loop rendering.
School Materials Platform
Problem: Students and teachers lacked a centralized, mobile-friendly platform to share and access curriculum content.
Solution: Built a mobile app and backend API for uploading, organizing, and searching educational materials with role-based access for teachers and students.
Tailor Marketplace App
Problem: Tailors had no digital channel to showcase portfolios, manage orders, and coordinate with customers.
Solution: Two-sided marketplace app pairing customers with tailors, featuring custom measurement flows, order tracking, and in-app messaging.
Housinn — Real Estate App
Problem: Property seekers in East Africa lacked a curated, mobile-native discovery platform for rentals and sales.
Solution: Flutter real estate app with map-based search, advanced filters, property listing management, and agent contact flows.
Technical toolkit
Grouped by domain. Production-validated across real enterprise and consumer systems.
Mobile Development
Backend Systems
Architecture
DevOps & Delivery
Explore my work on GitHub
Browse repositories covering Flutter apps, backend utilities, and open source experiments. Most of my production work is private, but my public repos reflect how I think about code structure, clean architecture, and system design.
What clients say
"Worked with Nicholas on my Sports games app and honestly had a great experience. Super easy to communicate with, clearly knows his stuff when it comes to Flutter, and always delivered on time. Definitely recommend him if you're looking for someone solid to build your app."
"Nicholas has great sense of attention to detail and great clarity of thought. He takes up everything he does very seriously with no half measures. He has very sound technical knowledge and is great in leading large teams."
"Nicholas has been an exceptional asset to the Housinn project. His attention to detail, strong problem-solving skills, and commitment to delivering quality work played a key role in bringing the Housinn app to life. I would recommend."
"It was a pleasure working with Nicholas. His attention to detail and innovative thinking played a pivotal role in helping us meet the deadline for our app. Thanks to his contributions, we successfully developed the MVP within the intended time frame."
Let's work together
Open to senior engineering roles, consulting engagements, and interesting technical problems.