Lars Melchior, Developer in Berlin, Germany
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Lars Melchior

Verified Expert  in Engineering

Full-stack Developer

Berlin, Germany
Toptal Member Since
July 15, 2020

Lars is a physicist, entrepreneur, and full-stack developer with 10 years of experience. Having built his own startup from scratch, he knows how to rapidly develop an MVP and bring a product to market. As an open-source library developer, he writes clean and maintainable code that's efficient and production-ready. Holding an MSc in physics, his strong research and analytical skills make him a valuable asset in almost any domain.


Freelance Clients
JavaScript, TypeScript, React, React Native, Expo, Styled-components, REST...
CSS, Mobile Development, Test-driven Development (TDD), Git, Full-stack...
Python, PyTorch, Flask, Flask-RESTful, React, Styled-components, Poetry...




Preferred Environment

Git, GitHub, Slack, SSH, Bash, Zsh, Visual Studio Code (VS Code), Xcode, Linux, MacOS, Emscripten, Jupyter Notebook, Python, Matplotlib, SciPy, NumPy, Fastlane, React Native, React, Express.js, Node.js, JavaScript, TypeScript, CMake, C++

The most amazing... I've built is Maphi, a math learning app that uses an innovative drag and drop interface to help anyone understand algebra intuitively.

Work Experience

Senior Full-stack Developer

2020 - PRESENT
Freelance Clients
  • Built the recruitment app for a large government body that helps candidates understand and prepare for the screening process. It included gamified exercises to help candidates evaluate their mental and physical conditions for the role.
  • Helped an educational platform understand and solve performance issues on their web platform, assisting them drastically in reducing their initial response time.
  • Developed a chrome extension that added much-desired extra features to third-party networking websites, which integrated perfectly into their existing UI.
  • Helped investors estimate the technological value of one of their portfolio projects.
Technologies: JavaScript, TypeScript, React, React Native, Expo, Styled-components, REST, REST APIs, Optimization, Node.js, Chrome, Chrome Extensions, iOS, Android, Software Engineering

Co-founder and Full-stack Developer

2018 - PRESENT
  • Conceptualized, built, and released Maphi, the cross-platform mobile app for learning and practicing algebra using intuitive drag-and-drop gestures.
  • Built an algebra system based on commutative and associative pattern matching, specializing in manual interaction and generating step-by-step solutions to mathematical problems.
  • Developed a platform-independent game engine in OpenGL and C++ with bindings to SDL, React Native, and WebAssembly, supporting 2D vector rendering and multi-touch input.
  • Built the company's website at and an interactive browser math engine at
  • Implemented app analytics and A/B testing using Firebase.
  • Won several startup pitch competitions and secured a pre-seed investment funding round.
Technologies: CSS, Mobile Development, Test-driven Development (TDD), Git, Full-stack, WebAssembly, Fastlane, Firebase, React Native, React, Node.js, TypeScript, JavaScript, CMake, C++, Parsers, Refactoring, Concurrent Programming, OpenGL, OpenGL ES, REST APIs, iOS, Android, Software Engineering

Scientific Software Engineer

2021 - 2022
  • Developed the company's infrastructure to run experiments on the main MRI prototype. Experiments were run in a dynamic, full-stack application, driven with a RESTful server written in Flask and a dynamic front end written in React.
  • Built the infrastructure for measuring magnetic fields with high precision, requiring controlling a robot and Tesla Meter, using serial port communication and optimization algorithms for accurate localization and corrections.
  • Built C++/Python drivers for the MRI prototype's easy configuration, communication, and synchronization of the DAC/ADC cards for sequence controlling and data acquisition.
  • Derived and implemented algorithms for the noise canceling used to increase the signal-to-noise ratio on the MRI prototype.
  • Incentivized and helped the software team implement many software development best practices to create more stable and reliable software. These included continuous integration, type systems, linters, code reviews, etc.
Technologies: Python, PyTorch, Flask, Flask-RESTful, React, Styled-components, Poetry, TypeScript, Full-stack, Robotics, Hardware, Research, C++, Analog-to-digital Converters (ADC), Digital-to-analog Converters (DAC), Soldering, Electronics, SciPy, NumPy, PyBind11, Refactoring, Concurrent Programming, SQLite, Physics, Git, REST APIs, Mypy, Software Engineering

Student Research Assistant

2011 - 2017
Geog-August Universität Göttingen
  • Designed, implemented, and published the X-ray optics simulation toolkit, PyPropagate, for performing static and time-resolved X-ray high wave propagation simulations.
  • Participated in and evaluated synchrotron experiments with results published as papers in the Journal of Applied Crystallography and Optics Express.
  • Ported evaluation and visualization frameworks written in MATLAB to C++ and Python, obtaining much better performance and using only FOSS.
  • Tutored physics undergraduates in programming courses, teaching and evaluating their C++ and numerics skills.
Technologies: Git, SciPy, NumPy, Matplotlib, SymPy, LaTeX, Mathematica, MATLAB, LLVM, Setuptools, Python, CMake, C, C++, Physics, Software Engineering

Maphi is a cross-platform mobile app for learning and practicing mathematics through intuitive drag-and-drop gestures. I conceptualized and implemented most of the app, consisting of a custom math manipulation engine written in C++, OpenGL, and a custom DSL. Platform-dependent components were added using React Native. I also built the company's website using React and Gatsby, and the online implementation of the math engine, using WebAssembly.

The ModernCppStarter project is one the most popular starter projects for C++ development, thanks to its simplicity and feature richness. It shows that developing large and modular C++ applications with large codebases can be made simple using a declarative approach to build systems and package management. I created the projects and am its core maintainer.

Created the CPM.cmake package manager for the CMake build system to help simplify the complexity involved in managing dependencies in large C and C++ projects. Thanks to a simple API and flexibility, it greatly simplifies the CMake development process and is now used in thousands of projects by developers around the globe, including companies such as NVIDIA and Microsoft.

PyPropagate is a 2D, 3D paraxial wave propagation framework that I built for the Institute for X-Ray Physics in Göttingen. It allows the user to set up a simulation in arbitrary precision, using a hand-crafted computer algebra system and JIT compilation. As far as I know, it is the first framework for time-resolved paraxial wave propagation, and it has been published in Optics Express, the popular scientific journal.


LarsPlot is a scientific application for 2D data visualization that I developed for the App Store in 2011. In addition to creating many types of beautiful plots of external data, the project includes an RKF45 solver for systems of nonlinear differential equations to generate visualizations of physical systems.

Fit | The Nonlinear Regression App

Fit is an elegant and fast curve-fitting application that I designed for the App Store in 2012. The app implements the Levenberg-Marquardt algorithm and finds the best-fit parameters for a given dataset.
2013 - 2017

Master's Degree in Physics

Georg-August Universität Göttingen - Göttingen, Germany

2009 - 2013

Bachelor's Degree in Physics

Georg-August Universität Göttingen - Göttingen, Germany


React, NumPy, Mypy, Node.js, SciPy, Matplotlib, OpenGL, OpenGL ES, REST APIs, Setuptools, SymPy, PyTorch, Flask-RESTful, Quartz 2D


Git, Slack, GitHub, LaTeX, CMake, Apple Motion, Affinity Designer, Adobe Photoshop, Emscripten, Asana, Xcode, MATLAB, Mathematica, Fastlane, Zsh, Expo


React Native, Express.js, Flask, Next.js, Angular, Chrome


C++, TypeScript, Python, Objective-C, Lua, JavaScript, CSS, HTML, Bash, C, Kotlin


Unit Testing, Refactoring, Concurrent Programming, Test-driven Development (TDD), Mobile Development, Gamification, REST


Firebase, Android, iOS, MacOS, Linux, Jupyter Notebook, Visual Studio Code (VS Code)


MongoDB, MySQL, SQLite, PostgreSQL


Mathematics, Physics, Computational Physics, Science, Numerical Simulations, Biophysics, Computer Algebra Systems, Visualization, Physics Simulations, Computational Biology, X-ray Optics, Education Technology (Edtech), Full-stack, Genetic Algorithms, Research, Parsers, LLVM, Software Engineering, Computational Biological Physics, Neural Networks, Artificial Neural Networks (ANN), Gatsby, WebAssembly, Neuroscience, Startups, APIs, Minimum Viable Product (MVP), Mobile Apps, SSH, Machine Learning, Boost.Python, Styled-components, Poetry, Robotics, Hardware, Analog-to-digital Converters (ADC), Digital-to-analog Converters (DAC), Soldering, Electronics, PyBind11, Objective-C++, User Experience (UX), Algorithms, Numerical Methods, Optics, 3D Visualization, Dependency Management, Optimization, Chrome Extensions

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