Frédérique Mittelstaedt, Developer in London, United Kingdom
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Frédérique Mittelstaedt

Verified Expert  in Engineering

Software Developer

London, United Kingdom
Toptal Member Since
February 22, 2019

Frédérique is a software engineer and entrepreneur with an MSc in theoretical physics from Imperial College London. He excels at building full-stack systems with the web, desktop, and mobile apps, microservices, and external integrations. Frédérique co-founded an international marketing agency and three startups in developer tools, cybersecurity, and AI. Frédérique regularly releases TypeScript packages and contributes to other open-source projects.


Python 3, Apache Kafka, Flink, Apache Flink, Apache Airflow, RabbitMQ, Terraform
Python 3, Apache Flink, Flink, Apache Kafka, Terraform
Packer, Apache Airflow, Kubernetes, Docker, Redux, React, TypeScript...




Preferred Environment

Git, Visual Studio Code (VS Code), i3, Arch Linux, MacOS

The most amazing...

...system I've built can identify arbitrage trading opportunities between any pair of cryptocurrencies on 94 exchanges in real time (updated every few seconds).

Work Experience

Engineering Manager, Messaging Foundations

2022 - PRESENT
  • Established the messaging foundations team, its mission, charter, and technical and product roadmap.
  • Led the design and development of Reddit's centralized streaming platform based on Apache Kafka, Apache Flink, and Flink Stateful Functions.
  • Worked with cross-functional teams to support their adoption of the streaming platform.
Technologies: Python 3, Apache Kafka, Flink, Apache Flink, Apache Airflow, RabbitMQ, Terraform

Engineering Manager, Real-time Safety Applications

2021 - 2022
  • Established the real-time safety applications team, its mission, charter, and technical and product roadmap.
  • Grew my team to four back- and front-end engineers.
  • Led the development of a stream processing platform based on Apache Kafka, Apache Flink, and Flink Stateful Functions.
  • Built a framework and tooling for developing streaming applications running on Kubernetes in Python.
  • Supervised the development of real-time safety applications.
  • Worked with cross-functional teams to support their adoption of the streaming platform.
  • Supervised the migration of a legacy real-time safety system to the new streaming platform.
Technologies: Python 3, Apache Flink, Flink, Apache Kafka, Terraform

Senior Software Engineer II

2020 - 2021
  • Implemented features for the main site and internal applications using TypeScript, React, Redux, Python, and SQLAlchemy.
  • Improved and upgraded the development tooling and workflow for several projects using TypeScript and Python.
  • Coordinated the scrum process and helped improve communication within and between teams as scrum master for two teams.
Technologies: Packer, Apache Airflow, Kubernetes, Docker, Redux, React, TypeScript, PostgreSQL, SQLAlchemy, Python

Freelance Software Engineer

2020 - 2020
The Boston Consulting Group (BCG)
  • Modified a web app to make it compatible with Internet Explorer 10+ and Microsoft Edge.
  • Added and configured Babel and necessary polyfills for a web app built using Create React App to make it work on IE and Edge using the customize-cra library.
  • Identified layout and performance issues using the browser profiling and implemented fixes to improve performance on IE and Edge.
Technologies:, Babel, MobX, React, JavaScript

Freelance Software Engineer

2019 - 2020
  • Implemented features for the main site and internal applications using TypeScript, React, Redux, Python and SQLAlchemy.
  • Improved and upgraded the development tooling and workflow for several projects (TypeScript & Python).
  • Coordinated the scrum process and helped improve communication within and between teams as scrum master for two teams.
  • Transitioned to a full-time position as a senior software engineer in May 2020.
Technologies: Packer, Apache Airflow, Kubernetes, Docker, Redux, React, TypeScript, PostgreSQL, SQLAlchemy, Python

Freelance Software Engineer

2019 - 2019
  • Refactored the app offering a shareable podcast web page with general info, links and the latest episode extracted from an RSS feed (built using Nuxt.js, Vuex, and Vue.js in JavaScript).
  • Added an episode-list page to with an expandable collection of all episodes of a podcast and an HTML 5 audio player that sticks to the bottom of the screen to play each episode (including a popover to set the playback speed).
Technologies: Nuxt.js, Vuex, Vue, JavaScript

Freelance Software Engineer

2019 - 2019
  • Developed a translator web app for ExxonMobil's global intranet using TypeScript, React, MobX with C# Azure functions; the back end was deployed on Microsoft Azure.
  • Led weekly catch-up meetings with ExxonMobil teams in the US and Malaysia and provided technical guidance for project architecture and feature implementation.
  • Rewrote an initial application prototype from JavaScript to TypeScript and configured all of the build tools.
  • Implemented a React component library for ExxonMobil's design system, Unity.
  • Implemented a multiresolution React icon library (including tests) using code generation based on SVG source files.
  • Integrated the Microsoft Azure and Google Cloud private endpoint translation APIs with the web app for text translation.
  • Created a responsive application UI using React and the component libraries I created with support for switching between Microsoft Azure and Google Cloud APIs.
  • Integrated text-to-speech functionality using the Howler web audio library and the Azure Cognitive Services and Google Cloud text-to-speech APIs.
  • Implemented an Azure functions endpoint for translating Word documents, Excel spreadsheets, PowerPoint presentations and plain text documents in C# using the Office OpenXml library and the Azure and Google Cloud translation APIs.
  • Integrated authentication and access control using Azure Active Directory.
  • Implemented proxy endpoints for all API calls for authentication and performance monitoring using C# Azure functions.
  • Added support for Unicode input using an on-screen software keyboard.
  • Cleaned up and documented the codebase and documented the application architecture for future maintainers.
Technologies: Azure Text to Speech, Azure Functions, OpenXML, C#, MobX, React, TypeScript

Contract Software Engineer

2018 - 2019
  • Designed and built an IDE for creating and editing optimization problems/projects specified in the company's proprietary programming language.
  • Extended the Monaco editor powering Visual Studio Code with a custom theme, language definition, and syntax completion handlers.
  • Defined and implemented a custom project document file format.
Technologies: Electron, MobX, React, TypeScript

Contract Software Engineer

2018 - 2018
  • Built a crowdfunding web app for the Islamic Development Bank (
  • Refactored the Vue.js codebase and integrated the Vuex state management library.
  • Internationalized the back end and front end (supporting English, French, Arabic, Turkish, Bengali, Malay, Kazakh, and Indonesian).
  • Designed the build system for six country-specific microsites (each localized with different design, text, and media).
  • Helped launch the platform within 21 days of joining the team.
  • Built a second web app with information material for entrepreneurs in Kenya and Nigeria with country-, sector- and company stage-specific information pathways within seven days.
Technologies: PostgreSQL, Eve, Flask, Python, Vuex, Vue, JavaScript

Contract Software Engineer

2017 - 2018
Private Client
  • Developed a blockchain explorer and cryptocurrency accounting system for Bitcoin and Ethereum.
  • Implemented a method for efficiently tracking the flow of funds between different addresses.
  • Deployed the system on DigitalOcean using Docker.
Technologies: Ethereum, Bitcoin, React, MongoDB, TypeScript

Contract Software Engineer

2017 - 2018
Private Client
  • Built a system for the real-time detection of arbitrage opportunities between cryptocurrency pairs on 94 exchanges.
  • Designed the algorithm to calculate the relative and total profit opportunities from the spread, order books, the exchange, and transfer fees.
  • Created an efficient long/short hedging strategy to minimize fees and maximize processing speed.
  • Implemented a LINE messenger bot to send out notifications when opportunities are detected.
  • Deployed the system on AWS in an ECS cluster provisioned with Terraform.
Technologies: Amazon Elastic Container Service (Amazon ECS), Terraform, MongoDB, CCXT, TypeScript

Founder and CEO

2017 - 2018
  • Designed a programming and data language called Morph.
  • Implemented the initial runtime and interpreter for Morph in Python.
  • Installed a compiler for Morph using the LLVM compiler toolchain.
  • Developed a web-based runtime for Morph using TypeScript.
  • Designed and implemented the service- and component-oriented application framework Service.js in TypeScript.
  • Designed and implemented the React UI component library Service UI using TypeScript, React, and the CSS-in-JS library emotion.
  • Designed and implemented an extensible language- and framework-independent code generation library.
  • Designed an AI system for the auto-generation of source code for multi-application software systems from requirements.
  • Participated in the Zeroth.AI startup accelerator in Hong Kong in 2017.
Technologies: Python, LLVM, TypeScript

Co-founder | CEO

2014 - 2017
Global Graduate Marketing
  • Co-founded a digital marketing agency specializing in international graduate student recruitment with $500,000 annual revenue.
  • Executed short-term marketing boosts to increase applicant numbers for specific programs.
  • Implemented long-term marketing strategies, increasing applicant numbers by up to 2x-3x over three years.
  • Built a large and international network of online and offline advertising partners (e.g., journals, conferences, and PhD and Master search portals).
Technologies: Twitter, Facebook, Google AdWords, CSS3, HTML5, JavaScript

Co-founder and CEO

2015 - 2015
  • Implemented a user-friendly web-based UI for Ruuta's WiFi router operating system based on OpenWrt.
  • Developed partnerships with router manufacturers.
  • Took part in the first cohort of the CyLon cybersecurity accelerator.
  • Presented Ruuta at RISEConf in Hong Kong in August 2015.
Technologies: JavaScript, OpenWRT

Contract Software Engineer

2015 - 2015
  • Refactored the codebase and added features to a crowdfunding platform web app.
Technologies: jQuery, JavaScript, MySQL, Laravel, PHP


2014 - 2015
  • Built a template-based system for software development and deployment.
Technologies: JavaScript, Python

Student Assistant (Software Engineer)

2014 - 2014
BTC | Business Technology Consulting AG
  • Developed an inventory system using Java, Spring, and MySQL.
Technologies: MySQL, Spring, Java

Freelance Web Developer

2014 - 2014
smart insights GmbH
  • Developed the web version of the company’s tool for marketing research, "my opinion" with the functionality and design based on existing mobile apps.
  • Created a survey engine supporting different types of questions and views.
  • Integrated the UI with the company's pre-existing JSON API.
Technologies: JavaScript, PHP

Various Student Assistant Positions

2011 - 2014
Jacobs University Bremen
  • Organized events, handled technical repairs and installations, and administered to the Joomla website of the Alfried-Krupp-College (residential hall) as part of the college office team from Oct 2011 to Dec 2012.
  • Supervised the public usage hours of the computer lab of the CLAMV laboratory (Computational Laboratory for Analysis, Modeling, and Visualization) from Sep 2011 to Dec 2013.
  • Created the design, added content, and deployed the WordPress website of the Research Center Humanities, Modernity, and Globalization (HMG) prior to its opening conference in Jun 2011.
  • Developed an online event planning system in PHP that is synchronized with an exchange calendar and integrates user login with an LDAP directory in Aug 2012.
  • Developed the news carousel on the front page of the main university website and the slide show of the graduation 2013 microsite using jQuery from May 2013 to Jun 2013.
  • Built a mobile-ready web app providing updated meal plans and collecting meal reviews for the university catering services in Aug 2013.
  • Set up the computer lab and software for a workshop of the Basin and Petroleum System Dynamics Executive MSc program in Aug 2013.
  • Created a graphical visualization tool for complex polynomials using Newton’s method for Mac OS X using Objective-C and Cocoa from Oct 2013 to Jan 2014.
  • Developed a web application and data mining back-end for the analysis of search results from Google Search and Google Scholar and the semantic analysis of the search results from Nov 2013 to Jan 2014.
Technologies: Cocoa, Objective-C, Linux, LDAP, PHP, jQuery, JavaScript, CSS, HTML, Joomla

Freelance Typesetter

2012 - 2012
Prof. Birgit Mersmann
  • Handled the typesetting of the client's postdoctoral thesis “Schriftikonik. Bildphänomene der Schrift in kultur- und medienkomparativer Perspektive.”.
  • Converted the initial manuscript from Microsoft Word to LaTeX.
  • Added support and configured the packages for supporting contemporary CJK and several ancient scripts.
  • Manually corrected typesetting and formatting issues in a document with more than 200 pages.
Technologies: LaTeX

Student Assistant

2012 - 2012
Fraunhofer Institute for Open Communication Systems (FOKUS)
  • Built a library for recognizing arbitrary cameras and capture cards; also configured camera parameters, and accessed image data using Microsoft DirectShow in C#.
  • Developed calibration routines for multicamera systems.
Technologies: DirectShow, C#

Software Engineering Summer Intern

2011 - 2011
Fraunhofer Institute for Computer Architecture and Software Technology (FIRST) Internship Company NameFraunhofer Institute for Computer Architecture and Software Technology (FIRST)
  • Created a library and sample applications for 3D gesture control of a digital dome using Microsoft Kinect and OpenNI.
Technologies: OpenNI, Microsoft Kinect, C#, C++

Intern (Research)

2009 - 2009
DESY (German Electron Synchrotron)
  • Set up and executed a continuously running two-week-long experiment to measure the weather-dependent intensity of cosmic rays and determine the half-life of muon particles using plate detectors and a weather station.
Technologies: Weather

Intern (Research)

2009 - 2009
Humboldt University of Berlin
  • Evaluated and visualized data on Z^0 resonance from the LEP experiment at CERN using C++ and the Root data analysis framework.
Technologies: Root Cause Analysis, C++

IGLU eLearning System

During my first major solo web development project in 2010 and 2011, I created a modular eLearning system, IGLU, for my high school using PHP which I eventually extended with features for a broader audience.

I presented it at the German youth science competition “Jugend forscht” and subsequently won the Berlin state competition in the category: work environment.

Cryptocurrency Trading Platform

In autumn 2016, I created with a friend from university a cryptocurrency-trading platform and bot for personal use on the Kraken exchange.

In this (largely educational) project, we learned a lot about time series prediction, technical analysis as well as the microservice development and deployment (and we even made a small amount of profit).

CMS Administration and Theme Development

Starting in 2007, I administered to the website of my high school for about four years. This included migrating all of the media and content from an older CMS to Joomla, configuring the system, and developing a custom theme and some custom extensions for it. I initially taught myself HTML, CSS, and JavaScript primarily for this.

During my final two years in high school, I was a STEM ambassador and youth coordinator for the German STEM organization "MINT Zukunft schaffen" and, among other things, set up and managed a PHP-based forum system for them.

During my undergraduate studies, I also managed the CMS of my residential halls and worked on the main university WordPress website as well as event- and department-specific microsites. I managed the site content, created themes, extensions, and specific widgets—like an HTML 5 news carousel for the front page of the main university website replacing a previous Flash version.

MobX Emotion Theme Provider
This NPM package provides a component that observes a MobX store and injects the contents as a theme into the CSS-in-JS style library emotion. You can use it to make the theme dynamic and make all UI elements rerender, whenever the observable theme components update.

Responsive React Monaco Editor
This NPM package provides a responsive React component wrapping the Monaco Editor. Monaco is an open source editor powering Visual Studio code but, by default, it is displayed with a fixed width, specified initially. This component wraps the editor and makes it resize whenever the available space changes/the browser window resizes so it becomes useable for responsive design.

GitHub Pages Boilerplate
GitHub Pages is a free service for hosting static websites from a GitHub code repository. While commonly used for static content like code documentation, you can host entire single-page web apps on it.

This small project provides the boilerplate for building a React single-page web application using TypeScript and Webpack and deploying it to GitHub Pages with a single command.

TypeScript Error
This NPM package provides an extendable error class with support for TypeScript. Regular in-built JavaScript classes are not extendable like user-defined classes. To complicate matters, the behavior differs across browsers and support version of JavaScript.

This extendable error class is compatible across all browsers (including all version of IE) and has the behavior of the error classes in the latest version of JavaScript.

Tenor I at London Contemporary Voices Kin Choir
I was part of London Contemporary Voices Kin Choir from its formation in 2014 until I left London to become a digital nomad in 2016. Our repertoire was mainly focused on modern arrangements with experimental elements and vocal percussion (beatboxing).

We frequently have paid bookings at events and perform live with or do session recordings with professional artists like Kim Wilde, Shlomo, or Imogen Heap. During the summer, we perform at a number of music festivals in the UK and continental Europe.

Beyond just singing, I've also written choral arrangements of electronic music tracks and performed them with LCVK, such as "Monument" by Röyksopp & Robyn (linked) which now has nearly 16,000 views on Youtube (Feb 2019).

Digital Nomad

After completing my master’s degree, I decided to become a digital nomad, sold most of my belongings and left London to travel around the world.

I spent most of my time abroad in Thailand, Vietnam, Japan, and New Zealand, but also traveled to Myanmar, South Korea, the US, and the Caribbean.

While abroad, I studied different programming language implementations as well as textbooks and research papers on programming languages, compiler design, and artificial intelligence which ultimately led to me starting work on my third tech startup, Automorph.

Service.js Application Framework

Service.js is an application framework written in TypeScript for the JavaScript ecosystem.

The core idea behind service.js is to structure applications as asynchronously communicating services, which encapsulate some part of the application functionality. The communication between the services is described using strongly typed, reusable protocols.

The services can then run in locally, in parallel, or remotely without any changes to the codebase. This renders changes to the application deployment trivial. The same services can be used in a standalone application, in a monolithic client-server backend or using microservices.

I started this project to simplify the development of microservice-based applications using TypeScript. The framework is currently under development and I hope to release version 1.0 in the first half of 2019.

Service.UI Component Framework

Service.UI is a design and UI component framework written in TypeScript. The core idea is to use a design system for developing a component library for each project/application. The component structure follows the ideas of atomic design.

Service.UI currently uses the CSS-in-JS library emotion for theming and provides React components. The libraries are very small and each component, typically measuring less than 1KB in size each, can be used independently of the others, allowing overall bundle sizes to stay small.

Since the same concept can be applied to different environments, the library will be ported to React Native to support usage in mobile apps and Snabbdom which offers a faster and more lightweight alternative to React.

I started developing the development of this library due to the lack of good, small and easily configurable component libraries. The library is currently under development and I plan to release a stable version 1.0 in the first half of 2019.

Synaptic Wall

As part of an interdisciplinary team of students, I worked on the development of an interactive tool for drawing and simulating nodal networks, which were modeled after biological neural networks using processing.


ECMAScript (ES6), TypeScript, JavaScript, Python 3, HTML5, CSS3, Python, HTML, CSS, Sass, SCSS, YAML, PHP, SQL, Objective-C, Swift, Java, C, C++, C#, Scheme, Delphi, IDL


Express.js, Bootstrap, Svelte, Bulma, Electron, Spring, Cocoa, Redux, Flask, React Native, Laravel, OpenNI, Microsoft Kinect, Nuxt.js


REST APIs, React, Snabbdom, Node.js, MobX, Emotion Library, NumPy, Matplotlib, Chai, TensorFlow, LSTM, Google AdWords, SQLAlchemy,, SciPy, D3.js, CCXT, DirectShow, jQuery, jQuery UI, Kraken, Vuex, Rollup.js, Vue


Jira, Docker Compose, Docker Hub, Adobe Illustrator, Gulp, Adobe Photoshop, LaTeX, Mongoose, Adobe Creative Suite, NGINX, Mocha, Webpack, Webpack 4, Webpack 3, Jupyter, i3, Git, Bitbucket, Apache Airflow, Babel, Vagrant, Packer, Terraform, Adobe InDesign, Amazon Elastic Container Service (Amazon ECS), Amazon Elastic Container Registry (ECR), Moodle, Ansible, Apache, Geth (go-ethereum), Travis CI, CircleCI, Code Climate, Rollup, Codecov, Flink, RabbitMQ


RESTful Development, Functional Programming, Functional Reactive Programming, Object-oriented Programming (OOP), Agile Software Development, Continuous Integration (CI), Continuous Deployment, Continuous Delivery (CD), DevOps, Siamese Neural Networks, Test-driven Development (TDD)


Amazon Web Services (AWS), Linux, MacOS, Docker, DigitalOcean, Arch Linux, Alpine Linux, Azure, Visual Studio Code (VS Code), Twitter, OpenWRT, Azure Functions, Windows, iOS, Android, Kubernetes, Amazon EC2, Linode, WordPress, Joomla, Ethereum, Apache Flink, Apache Kafka


JSON, MySQL, MongoDB, Redis, OpenXML, PostgreSQL, Amazon S3 (AWS S3)


Design Systems, Front-end Development, Full-stack, Leadership, Technical Leadership, Mobile Apps, CTO, CSS-in-JS, Styled-components, Software Development, Embedded Software, Serverless, IT Security, SVG, ParcelJS, Artificial Neural Networks (ANN), Backpropagation, Deep Learning, Neural Networks, Deep Neural Networks, Hyperparameters, Hyperparameter Optimization, Machine Learning, Learning Transfer, Multi-task Learning, Facial Recognition, Convolutional Neural Networks (CNN), Neural Style Transfer (NST), Recurrent Neural Networks (RNNs), Long Short-term Memory (LSTM), LSTM Networks, Eve, Facebook, Root Cause Analysis, Weather, LDAP, Azure Text to Speech, LLVM, Bitcoin, Bitcoind, Chrome Extensions, Web Extensions, Scraping, Web Scraping, AWS DevOps, Semantic Technology, Snyk

2015 - 2017

Master of Science (MSc) Degree in Theoretical Physics (Quantum Fields and Fundamental Forces)

Imperial College London - London, United Kingdom

2011 - 2014

Bachelor of Science (BSc) Degree in Physics

Jacobs University Bremen - Bremen, Germany


Deep Learning Specialization



Sequence Models



Convolutional Neural Networks



Structuring Machine Learning Projects



Improving Deep Neural Networks: Hyperparameter tuning, Regularization and Optimization



Neural Networks and Deep Learning



Certified Scrum Product Owner® (CSPO®)

Scrum Alliance®


Certified Scrum Master® (CSM®)

Scrum Alliance®

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