Holger Schmitz, Developer in Didcot, United Kingdom
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Holger Schmitz

Verified Expert  in Engineering

Full-stack Developer

Location
Didcot, United Kingdom
Toptal Member Since
July 19, 2018

Holger has over two decades of experience in developing and implementing large-scale codebases. He is proficient in JavaScript, PHP, C++, Java, and PHP. He has worked in teams of varying sizes, and he enjoys taking on new challenges. Holger believes that the keys to success when working remotely with a client are good communication and clear project goals.

Portfolio

Reddit, Inc.
JavaScript, Front-end Development, HTML, TypeScript, Front-end, CSS, GraphQL...
Usable Machines, Inc.
Node.js, Microservices, Back-end, APIs, TypeScript, RPC, Apache Kafka...
Pampered Chef - E-Commerce
Angular, Node.js, JavaScript, TypeScript, HTML, CSS, Express.js...

Experience

Availability

Full-time

Preferred Environment

Git, Linux, Visual Studio Code (VS Code), TypeScript, C++, MacOS

The most amazing...

...thing I've developed was Schnek, a C++ library for simulations on large-scale clusters.

Work Experience

Senior Software Engineer

2023 - 2024
Reddit, Inc.
  • Implemented new landing experiences that provide cross-promotion between the website and the mobile app. The goal of this project was to improve the user experience of existing popups while maintaining conversion.
  • Created the events from the front-end and server-side rendered content that allowed the data team to perform A/B testing.
  • Tracked progress of tasks and bugs using Jira and Confluence.
Technologies: JavaScript, Front-end Development, HTML, TypeScript, Front-end, CSS, GraphQL, ECMAScript (ES6), Angular, React, REST, Vue, Polymer, Lit, Git, Jest, Docker, Tailwind CSS

Node.js/Full-stack Developer

2023 - 2023
Usable Machines, Inc.
  • Implemented a REST API for enterprise customers based on Express and tRPC.
  • Integrated the back end with AI services like OpenAI GPT, Google BERT, Microsoft Tapex, etc.
  • Improved existing code quality by adding unit tests and enforcing coverage.
  • Planned quality and performance metrics from a product owner viewpoint.
  • Implemented front-end components using React and Next.js. Made visual design decisions.
Technologies: Node.js, Microservices, Back-end, APIs, TypeScript, RPC, Apache Kafka, Artificial Intelligence (AI), LangChain, Pinecone, OpenAI GPT-3 API, Next.js, Prisma, Git, Full-stack, Full-stack Development

Full-stack Developer

2021 - 2023
Pampered Chef - E-Commerce
  • Developed a new shopping experience using microservices based on a complex business structure.
  • Took responsibility for designated packages and services. and decided on architecture guidelines and code quality standards.
  • Deployed and launched the new shopping experience and provided technical support.
  • Fixed bugs that had an impact on the business with fast turnaround times.
  • Managed ongoing work and bugs using Jira and agile processes.
Technologies: Angular, Node.js, JavaScript, TypeScript, HTML, CSS, Express.js, Amazon Web Services (AWS), MongoDB, CSS3, JavaScript 6, HTML5, Java, Front-end, APIs, Back-end, MEAN Stack, Unit Testing, GitHub, Software Design, Figma, Full-stack, Microservices, Data Structures, Git, Full-stack Development

Technical Writer

2018 - 2022
Okta, Inc.
  • Developed various applications using Angular, React, NextJS, and other technologies.
  • Implemented single sign-on authentication using the Okta libraries.
  • Documented the source code and wrote numerous tutorials.
Technologies: JSON Web Tokens (JWT), OAuth 2, REST APIs, Angular, React, CSS3, Sass, Front-end, MERN Stack, GitHub, Firebase, Git

Lead Developer

2011 - 2022
Cogito Learning, Ltd.
  • Designed and implemented financial risk analysis software for www.epsilon-risk.com.
  • Designed and implemented REST APIs for web and mobile applications.
  • Designed and developed an Android app for GCSE maths training.
  • Built a library for parsing and manipulating mathematical expressions and created an Android app for calculating and explaining mathematical derivatives.
  • Implemented a WordPress tracking system for recording links to external resources.
  • Extended a shopping cart system to allow highly customized products.
  • Constructed an Android app for calculating and explaining mathematical derivatives.
  • Implemented a WordPress theme framework for responsive single-page websites and created a React-based extension for the WordPress dashboard.
  • Implemented various websites from mockups in Figma.
  • Created a database abstraction layer in C++ to work with different SQL databases.
Technologies: C++, CSS, HTML, Java, PHP, Angular, React, Node.js, JavaScript, MongoDB, Material UI, Sass, Front-end, Back-end, MEAN Stack, PostgreSQL, MERN Stack, Unit Testing, Mobile App Development, GitHub, Architecture, Software Design, Mathematics, Quantitative Modeling, Full-stack, Data Structures, Git, Full-stack Development

Full-stack WordPress Developer

2020 - 2021
Clorox
  • Worked on multiple sites across the Clorox brand to provide updates to the CMS and implement changes in the front end. Sites include Glad.com, Hiddenvalley.com, Kingsford.com, and others.
  • Performed accessibility audit of all sites of the Clorox brand.
  • Converted smaller sites to static site generators Eleventy and Next.js. Sites include Hiddenvalleyranch.ca, Liquidplumr.com.au, Chux.com.au, and others.
Technologies: PHP, WordPress, Twig, Node.js, Elevate API, Next.js, HTML, CSS, jQuery, Full-stack, HTML5, Sass, Front-end, Unit Testing, Figma, Git, Full-stack Development

Full-stack JavaScript/Angular Engineer

2019 - 2020
Pampered Chef
  • Implemented the front-end experience in Angular from mockups.
  • Created back-end endpoints using Node.js/Express.js.
  • Composed unit tests with 100% code coverage.
  • Participated in regular stand-up and sprint meetings.
  • Participated in code reviews.
Technologies: Jenkins, Express.js, Node.js, Angular, TypeScript, JavaScript, MongoDB, Full-stack, HTML5, Front-end, APIs, Back-end, MEAN Stack, Unit Testing, GitHub, Figma, Microservices, Data Structures, Git, Full-stack Development

Lead JavaScript Developer

2018 - 2020
Push Technology, Ltd (now Diffusion Data)
  • Maintained a JavaScript client system that communicates with a server through WebSockets.
  • Implemented new features in the JavaScript part of the product.
  • Converted the existing JavaScript codebase to TypeScript.
  • Fixed bugs in the code as they appeared in a timely manner.
  • Updated the build process using Maven and Gulp.js.
Technologies: Gulp, Apache Maven, Jenkins, WebSockets, React, Node.js, TypeScript, JavaScript, JavaScript 6, APIs, Unit Testing, GitHub, Software Design, Data Structures, Git

Theoretical Physicist

2013 - 2018
STFC, Rutherford Appleton Laboratory
  • Implemented numerical algorithms in C++, Python, and MATLAB.
  • Created large-scale simulation codes using MPI.
  • Supported large-scale simulation packages.
  • Designed and implemented a library for grid-based simulations on large clusters.
  • Built tools for working with large datasets.
  • Implemented a reader and converter for proprietary data format.
  • Integrated systems of differential equations using various methods.
  • Implemented automatic symbolic manipulation of mathematical systems using Mathematica.
  • Created a web-based automatic formula book based on React.
  • Developed a parser for a C-style declarative language.
Technologies: Mathematica, MATLAB, Python, JavaScript, C++, Architecture, Mathematics

Pampered Chef

https://www.pamperedchef.com/
Pampered Chef is a marketing company selling food products and kitchen utensils. I was a full-stack developer working in a team. I was tasked with extending the functionality and resolving issues. The technology stack was based on Node.js, Express.js, and Angular 7.

The workflow was based on Agile principles with daily standup and biweekly sprints.

Diffusion JavaScript Client

https://www.npmjs.com/package/diffusion
As the senior JavaScript engineer for Push Technology (Pushtechnology.com), I was responsible for porting their Diffusion client from JavaScript to TypeScript, implementing new features, and fixing bugs.

The Diffusion Intelligent Data Platform™ synchronizes, manages, and distributes data among applications, devices, and systems via the web, mobile, and satellite networks.

Frmlae

This is an online formula book.

PROJECT SPECIFICS
• Front end: A single-page application using Angular 7, RxJS, and Material Design.
• Back end: A REST API using Node.js, Express.js, and MongoDB.
• Deployment: Used Digital Ocean Ubuntu 18.04 Droplet.

React Solitaire Demo

https://celebrated-daifuku-af55d3.netlify.app/
This is a demo written in my spare time showcasing some of my React skills. It is a Solitaire Game with a flexible rule system. Game rules can be specified as JSON-like objects, which allows me to add more games easily. The drag-and-drop feature for the playing cards has been implemented from scratch using no external libraries.

Tutor Scout

http://tutorscout.co.uk
I worked as the lead product developer of a platform that matches students with tutors. I analyzed the requirements and chose the technology stack that consisted of PHP, MySQL, Apache, and the PRADO framework. I also implemented the front end and back end.

Schnek

https://github.com/holgerschmitz/Schnek
Schnek is a C++ library for developing parallel simulations on Cartesian grids.

FEATURES
• Set up a file reader with C-style syntax.
• Implemented extendable formulas in the setup files.
• Constructed a hierarchical structure of simulation components.
• Possesses multidimensional grids.
• Initialized the grid from formulas in a setup file.
• Contains boundary cells and ghost cells.
• Provides MPI support for parallelization.
• Installed an MPI update of ghost cells to neighboring processes.
• Contains easy-to-use parallel and serial HDF5 output of grids.
• Developed a literature reference system to encourage the collaborative development of large codes.

Financial Risk Analysis

https://www.epsilon-risk.com/
I designed and implemented a complete risk analysis framework. It has cash flow generation, pricing, and stress testing of financial products using C++ and QuantLib. The product was designed for high throughput.

Angular 7 and Node.js/Express.js Tutorial

https://developer.okta.com/blog/2018/10/30/basic-crud-angular-and-node
This tutorial guides the reader through the steps to produce a single-page CRUD application. It focuses on authentication, both in the front end and back end, using Okta single sign-on.

PROJECT SPECIFICS
• Front end: Used an Angular 7.0.2 release.
• Back end: Built with Node.js, Express.js, and TypeScript.

Moreland Accountancy

ROLE
Lead WordPress developer

TASKS ACCOMPLISHED
I developed a plugin that allows content editors to assemble pages based on pre-designed blocks. The plugin hooks into the edit post page and displays a React-based user interface with drag-and-drop functionality. I also implemented the design based on templates.

Languages

TypeScript, Sass, PHP, C++, JavaScript, CSS, HTML5, JavaScript 6, CSS3, Java, HTML, Bash, SQL, Python, GraphQL, ECMAScript (ES6)

Frameworks

ZURB Foundation, Angular, Next.js, Express.js, Boost, Bootstrap, Tailwind CSS, OAuth 2, Twig, Sails.js, JSON Web Tokens (JWT), Jasmine, Jest, Material UI, PRADO, Swagger

Libraries/APIs

Node.js, React, MPI, REST APIs, Elevate API, jQuery, Vue 2, Stripe API, RxJS, HDF5, Chai, Sinon.JS, Vue, Polymer, Lit

Tools

MATLAB, GitHub, Figma, Prisma, Atom, IntelliJ IDEA, PhpStorm, Git, Mathematica, Gulp, Apache Maven, NPM, Jenkins, CircleCI, Karma, MQTT, Apache, Mocha, SAP Hybris

Paradigms

MEAN Stack, Unit Testing, Microservices, High-performance Computing, REST

Platforms

Software Design Patterns, WordPress, Linux, Eclipse, Visual Studio Code (VS Code), Amazon Web Services (AWS), Firebase, NVIDIA CUDA, Oracle, AWS Lambda, Apache Kafka, MacOS, Docker

Other

WordPress Plugins, Full-stack, Front-end, APIs, Back-end, MERN Stack, Mathematics, Software Architecture, Data Structures, Full-stack Development, Cluster Computing, Architecture, Software Design, Quantitative Modeling, WebSockets, Statistics, Quantitative Finance, WordPress Themes, Mobile App Development, TCP/IP, Numerical Methods, Parsers, Okta, ECS, Drag & Drop, SVG, Algorithms, Data Compression, RPC, Artificial Intelligence (AI), LangChain, Pinecone, OpenAI GPT-3 API, Front-end Development

Storage

MySQL, PostgreSQL, MongoDB, Oracle SQL

1995 - 2000

PhD in Theoretical Physics

Ruhr University Bochum - Bochum, Germany

1989 - 1995

Diploma (Master's) Degree in Physics and Computer Science

Ruhr University Bochum - Bochum, Germany

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