Available for Select Freelance Missions

Marc SitzeSenior Frontend Lead & Full-Stack Engineer

Engineering high-performance AI web applications, resilient fintech payment portals, and scalable component systems that drive real business growth.

Explore Case Studies

4+ Years Experience

Fintech & AI Platforms

UTC+1 • EU & US Overlap

Proven Track Record with High-Growth Teams & Enterprise Platforms

Bubo AIFrontend Lead • AI Platform

Maviance PLCSoftware Engineer • Fintech Gateway

Warap WorkFullstack Lead • Gig Platform

AlaxioneMobile Engineer • HealthTech

PNTECFrontend Engineer • Digital Products

SweezFullstack Contractor

HackerRankVerified React Professional

Bubo AIFrontend Lead • AI Platform

Maviance PLCSoftware Engineer • Fintech Gateway

Warap WorkFullstack Lead • Gig Platform

AlaxioneMobile Engineer • HealthTech

PNTECFrontend Engineer • Digital Products

SweezFullstack Contractor

HackerRankVerified React Professional

Case Studies

Featured Case Studies

Real-world engineering solutions delivering measurable impact in AI, Fintech, and scalable web apps.

aiFrontend Lead

Bubo (France / Remote)2024 - 2025

Bubo AI

A revolutionary AI document archiving & management solution featuring instant vector search and GPT-style conversational retrieval.

< 350msQuery Retrieval Time

100k+Indexed Documents

+75%Task Efficiency

Next.js 15React 19TypeScriptTailwind CSS

View Case Study→

fintechSoftware Engineer

Maviance PLC2022 - 2024

Maviance Payment Gateway

Enterprise customer and merchant payment portal engineered to process high-volume corporate transactions securely across Central Africa.

$10M+Monthly Transaction Volume

99.4%Payment Success Rate

99.9%Uptime SLA

ReactTypeScriptNode.jsExpress

View Case Study→

marketplaceFull-Stack Engineer & Lead

Warap Work2023 - 2024

Warap Work

Bilingual (English & French) micro-jobs marketplace connecting task posters with verified gig workers across Africa and the diaspora.

100% EN/FRBilingual Localization

< 5sEscrow Milestone Speed

98/100Lighthouse Performance

Next.jsReactTypeScriptTailwind CSS

View Case Study→

mobileMobile Engineer

AfricaFix Logistics2023

AfricaFix Mobile

On-demand logistics and appliance repair service mobile app connecting homeowners with vetted technicians in real time.

60 FPSScreen Interaction Speed

InstantOffline Cache Sync

4.8 / 5Customer Rating

React NativeExpoTypeScriptReact Query

View Case Study→

See all projects

Turnkey Solutions

Packaged Engineering Services

High-leverage engineering leadership tailored for ambitious startups and enterprises looking to launch fast, scale securely, and dominate their category.

Popular for AI Startups

AI & High-Performance Web Apps

Ultra-fast Next.js 15 web apps integrated with real-time conversational AI & LLM workflows.

next-ai-stream.ts

Latency: 280ms

// Real-time streaming token pipeline

const response = await aiClient.streamQuery({

vectorIndex: "legal-docs-v2",

maxTokens: 4096,

optimisticUI: true

});

Sub-second Next.js 15 App Router architecture
Streaming RAG & conversational AI interfaces
Vector search integration (OpenAI, Pinecone)
Zero-latency optimistic UI with React 19

Best for: Funded AI startups, document intelligence, and SaaS founders.

Enterprise Grade

Fintech, Payments & High-Concurrency Systems

Resilient merchant gateways and high-volume transaction portals engineered for reliability.

Gateway Success Rate99.4%

Multi-Currency RoutingZero-Loss Idempotency

Multi-currency payment gateway integrations
High-concurrency merchant & customer portals
Idempotent API workflows & audit trails
Bank-grade security and compliance UI

Best for: Fintech scale-ups, payment processors, and enterprise portals.

Strategic ROI

Frontend Leadership & Design Systems

Pixel-perfect component systems, fluid 60FPS animations, and multi-lingual global scalability.

Tailwind CSS v4 & 21st.dev luxury design systems

GPU-accelerated GSAP & Framer Motion physics

Internationalization (EN / FR) with zero layout shift

Lighthouse 95+ performance optimization audits

Best for: Companies needing elite frontend leadership and polish.

Google Lighthouse Optimization Standard

Performance

100

Accessibility

100

Best Practices

100

SEO

Sub-second LCP • Zero Cumulative Layout Shift • GPU-Accelerated 60FPS

Career Milestones

Work Experience

Engineering leadership and scalable system delivery across global remote teams and high-growth ventures.

Frontend Lead (remote)

bubo

Jan 2024 — Jun 2025

a revolutionary document archiving and management solution. With advanced AI-based search and instant chat like GPT, find your information in an instant

Software Engineer

Maviance

Nov 2022 — Aug 2024

I played a key role in developing an innovative customer payment portal and restructuring the existing project. This platform was designed to simplify and secure the payment process, providing a seamless experience for users (merchant, corporate)

Software Developer

Gateway/Beone

Apr 2022 — May 2022

Developing Alaxione mobile patients which is an application that permits doctors to communicate with other doctors and patients through a mobile app

Software Developer

Gateway/Beone

Jan 2022 — Apr 2022

Developing Alaxione mobile patients which is an application that permits patients to book appointments with doctors through a mobile app

Software Developer

FREELANCE(remote)

May 2021 — Dec 2021

Working on random freelance projects, and dealing with specific tasks

Front-End Developer

PNTEC-LTD

Jan 2021 — Feb 2021

Project initialisation and setup, Creation of web interfaces from Adobe XD design and API integration from a headless CMS (Strapi)

Fullstack developer

REFRAICHE

Jan 2021 — Feb 2021

Creation of new web interfaces for the web app, Implementing new API features and integrating them in the front end, Integration of mobile payment methods and paypal