Matthias is available for hire
Hire MatthiasMatthias Leu
Verified Expert in Engineering
Shopify Developer
Chiang Mai, Thailand
Toptal member since April 30, 2024
Bio
Matthias is a lead engineer with 22 years of experience in full-stack architecture and a focus on the Shopify ecosystem. With a Master of CS from TUM and roots at Cap Gemini, he builds complex SPAs and robust middleware using Vue and Node.js. He leverages agentic workflows and MCP to accelerate development and slash OPEX. He recently engineered a 250+ section custom ecosystem, including Shopify apps for a global brand, replacing high-fee SaaS with proprietary code.
Portfolio
Scandinavian Biolabs ApS
Shopify Plus, Shopify API, Shopify Theme, Vue, Tailwind CSS, REST, GraphQL...
Croox Cross Over Experts
Nuxt.js, Vue, HTML5, React, CSS5, SQL, JavaScript, WordPress, REST APIs...
Dinnagan Garden Co. Ltd.
JavaScript, HTML5, CSS5, SQL, Vue, Go, CSS
Experience
- JavaScript - 12 years
- HTML5 - 12 years
- REST - 10 years
- Vue - 8 years
- Tailwind CSS - 6 years
- Node.js - 6 years
- Shopify Plus - 5 years
- Shopify Liquid - 5 years
Preferred Environment
Shopify Plus, Shopify Theme, Vite, Vue, Node.js, ChatGPT API, Agentic AI, API Integration, APIs, eCommerce
The most amazing...
...solution I've built is a Shopify AI diagnostic UI, using custom Vue and AWS-hosted vision models to deliver real-time diagnostics at scale.
Work Experience
Senior Shopify Engineer
2020 - PRESENT
Scandinavian Biolabs ApS
- Architected a high-performance, multi-region Shopify Theme 2.0 ecosystem using Vite, Tailwind CSS, and Alpine.js, maintaining architectural consistency and elite performance scores across five localized global stores.
- Developed a library of 250+ custom theme sections and Shopify apps with a React-based back end, enabling rapid Figma-to-code implementation and eliminating dependency on high-cost 3rd-party SaaS applications.
- Spearheaded the integration of server-side AI agent networks and Claude.md rule hierarchies to automate refactoring and testing, significantly accelerating the internal development lifecycle for five storefronts.
- Engineered a custom Vue-integrated application and built an API to an AWS-hosted computer vision model to deliver real-time, personalized hair health analysis and product recommendations directly within the Shopify interface.
- Introduced a Vite-based deployment pipeline using Shopify CLI, enabling sophisticated project bundling and secure deployments across a global multi-shop environment in seconds.
- Built a custom Vue customer portal to orchestrate complex subscription and order management, replacing legacy account areas and substantially reducing customer service operational load. Includes an API to multiple 3rd-party systems.
- Designed a secure Shopify app proxy to facilitate cryptographically signed API communication between front-end interfaces and five external CRM/ERP systems, enabling real-time data synchronization.
- Implemented a sophisticated discount engine using the Shopify Cart Transform API, allowing for complex, multi-layered promotional logic that bypassed native platform limitations.
Technologies: Shopify Plus, Shopify API, Shopify Theme, Vue, Tailwind CSS, REST, GraphQL, JavaScript, TypeScript, Liquid, HTML5, REST APIs, Node.js, CSS, ChatGPT API, Claude Code, Vibe Coding, AI Tools, PostgreSQL, Python, Agentic AI, APIs, API Integration, eCommerce, React, Agentic Coding, Artificial Intelligence (AI), Large Language Models (LLMs), User Experience (UX), Inventory Management
Senior Developer
2020 - 2023
Croox Cross Over Experts
- Architected a secure, Nuxt.js-powered medical data portal for a mobile healthcare ecosystem, enabling clinical analysis of patient wellness data via high-fidelity, reactive interfaces.
- Engineered a React-based plugin architecture for healthcare service management, facilitating complex room rental and space utilization services for clinical providers.
- Developed mission-critical middleware to synchronize PrestaShop and LexOffice, automating high-volume accounting and inventory data flows and eliminating manual administrative overhead.
- Implemented intricate frontend state management to ensure seamless data reactivity and security across sensitive healthcare and financial platforms.
Technologies: Nuxt.js, Vue, HTML5, React, CSS5, SQL, JavaScript, WordPress, REST APIs, Node.js, CSS
Full-stack Developer
2018 - 2020
Dinnagan Garden Co. Ltd.
- Architected a comprehensive farm management and resource tracking system for Maejo University, focusing on real-time data acquisition and analytical reporting for large-scale organic agriculture.
- Developed a high-performance Go REST API integrated with a reactive Vue front end to support complex data visualization and real-time field monitoring.
- Spearheaded iterative UI/UX improvements through direct collaboration with onsite stakeholders, ensuring high data integrity and system usability in diverse field environments.
- Designed a scalable data schema to manage complex resource interdependencies, providing the foundation for automated analytical reporting and long-term agricultural intelligence.
Technologies: JavaScript, HTML5, CSS5, SQL, Vue, Go, CSS
Senior Web Developer
2016 - 2017
BlackSnow ApS
- Led a comprehensive technical redesign and full-stack overhaul of a high-growth platform, prioritizing front-end optimization and back-end system scalability.
- Engineered a proprietary custom checkout experience that significantly improved conversion rates by streamlining complex user flows and reducing transactional friction.
- Managed the entire technical landscape and infrastructure scaling during a critical growth phase, ensuring architectural stability through to the successful acquisition of the company.
- Developed advanced storefront features and custom back-end integrations to enhance operational efficiency and maintain high-performance benchmarks across the digital ecosystem.
Technologies: CSS5, HTML5, PrestaShop, SQL, JavaScript, REST APIs, CSS
Development Manager
2013 - 2015
Arvixe
- Built a specific department offering web programming services to hosting customers to increase customer retention.
- Worked on more than 40 homepage use cases to implement customer websites.
- Grew the department to profitability within one year and a half.
Technologies: SQL, HTML5, CSS5, REST APIs, CSS
Web Developer
2011 - 2013
Media-Concept Bürobedarf
- Set up two online shops based on the PrestaShop framework.
- Implemented SEO strategies to increase visitor traffic.
- Built API integrations to the central .NET-based API, ensuring fault-free real-time order data synchronization.
Technologies: SQL, MySQL, SEO Tools, HTML5, PrestaShop, JavaScript, Search Engine Optimization (SEO), .NET, REST APIs, CSS
Senior Web Developer
2007 - 2010
COMP-MALL
- Set up, designed, and maintained the company's web presence and online shop for industrial computer hardware.
- Oversaw the entire online sales channel, supervising all related processes and implementations.
- Created APIs with Taiwanese manufacturers, collaborating with their IT side to automatically feed product information to the website.
Technologies: HTML, CSS5, JavaScript, CSS
Software Developer
2006 - 2007
Capgemini
- Handled the central data-entry business case implementation.
- Collaborated with the testing team to secure process integrity in a team of over 30 developers.
- Acted as the point of contact for the customer testing team, creating valuable solutions and improvements based on their input.
Technologies: Java
Experience
AI Hair Loss Detection Tool
I created a Shopify-embedded UI tool for visitors to upload photos of their hair and scalp. This solution analyzes images via an API to an AWS-based AI model that determines hair issues that can be treated with the company's products. This tool is a Vue-based UI with AWS API integration that sends photos to the AI model.
Vue Shopify Customer Portal SPA to Administrate Subscriptions and Orders
https://scandinavianbiolabs.com/accountThis project involved creating a Vue-based single-page application to replace the standard Shopify customer back end. It required REST and GraphQL API integration to the Shopify core and the recharge subscription services. The new implementation allows customers to add, swap, reschedule, change, cancel, remove, and skip products and subscriptions.
Shopify API Proxy App for 3rd-party API Integrations
This project involved developing a Shopify app that offers API endpoints through an app proxy, allowing front ends to use this API to securely communicate with 3rd-party services, including Klaviyo, AWS, ReferralCandy, and the Shopify API.
Shopify Quiz Component
A Vue-based Shopify theme component that allows a comprehensive quiz with dedicated question logic routing depending on user answers. At the end, the best-matching product is selected based on all answers, and hair treatment proposals are provided.
All customer data given is stored via Klaviyo API integration.
All customer data given is stored via Klaviyo API integration.
Shopify Vite Deployment Pipeline
I created a Vite-based Shopify theme deployment setup, enabling project bundling and deployment in seconds over multiple countries' shops. This resulted in a distinguished setup with dynamic imports to reduce JavaScript page load and individual script loads.
Medical Customer Data Analysis Dashboard
I developed a Nuxt-based back end to allow administrators to check statistical user mobile app submitted data on different graphical levels.
Graph representations leveraged Chart.js and included complex data range zooming. In addition, data storage was implemented through a Parse back-end server.
Graph representations leveraged Chart.js and included complex data range zooming. In addition, data storage was implemented through a Parse back-end server.
Complete Shopify Theme 2.0 Rewrite With Alpine Integration and Vite JavaScript Bundling
I created a Shopify Theme 2.0 from scratch based on a complex Figma design. For enhanced performance, I integrated Alpine as a TypeScript framework. I developed over 200 sections and UI snippets, writing all JavaScript components myself, including carousels and video control overlays, to avoid 3rd-party JavaScript overhead and ensure optimal page-load times.
Custom Shopify Discount App using Cart Transform API
A discount app bypassing the Shopify discount mechanism, which is limited to one product discount per cart line. Realizes custom implementation of targeted Upsell and BOGO discounts, which are infinitely stackable via Cart Transform API. Integrates with the theme cart and Checkout Extensions to make the user experience frictionless from PDP to Checkout.
Education
2004 - 2004
Diploma in Computer Science
National University of Singapore - Singapore
1998 - 2004
Master's Degree in Computer Science
Technical University of Munich - Munich, Germany
Skills
Libraries/APIs
Liquid, Vue, REST APIs, Shopify API, Node.js, React, Chart.js
Tools
Shopify Plus, Claude Code, PrestaShop, AWS IAM, NPM, Figma to HTML
Languages
JavaScript, HTML5, HTML, Shopify Liquid, CSS, TypeScript, Java, SQL, GraphQL, Go, Python
Frameworks
Tailwind CSS, Nuxt.js, Express.js, .NET
Paradigms
REST, Search Engine Optimization (SEO)
Platforms
Shopify, Parse Server, Visual Studio Code (VS Code), WordPress, Parse
Storage
MySQL, MongoDB, PostgreSQL
Other
Shopify Theme, Web Development, Full-stack, Vibe Coding, eCommerce, CSS5, Custom Shopify Apps, Vite, ChatGPT API, AI Tools, API Integration, APIs, Algorithms, SEO Tools, Enterprise Resource Planning (ERP), Computer Science, Agentic AI, Agentic Coding, Artificial Intelligence (AI), Large Language Models (LLMs), User Experience (UX), Inventory Management, Supabase
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