Lukasz Reszczynski, Developer in Umeå, Sweden
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Lukasz Reszczynski

Verified Expert  in Engineering

Full-stack Developer

Umeå, Sweden
Toptal Member Since
September 21, 2020

Lukasz is a UK-educated full-stack web application developer who has authored papers and patents in his field. Trained in computational astrophysics and bioinformatics, he has over a decade of experience developing enterprise software applications. All in all, Lukasz excels at turning a client's vision into reality.


Weaver Dating Inc.
Node.js, React Native, Apache Solr, Solr, Express.js, Sequelize
US-based biotechnology company (via Toptal)
Electron, OpenCV, Computer Vision, Computer Vision Algorithms, Python...
Partfiniti, Inc.
Redis, RabbitMQ, React, Git, Composer, Phinx, Ubuntu, HTML, Apache Solr, Solr...




Preferred Environment

Ubuntu, LAMP, Docker, PhpStorm, Command-line Interface (CLI)

The most amazing... I've created was a three-body simulation used to investigate the coalescence times of binary black holes subject to Kozai-Lidov oscillations.

Work Experience

Mobile App Developer | Contractor

2021 - 2022
Weaver Dating Inc.
  • Developed a React Native mobile application for iOS and Android.
  • Developed a back-end API in Node.js (Express.js) for the mobile application.
  • Developed and implemented a matching algorithm utilizing Apache Solr.
Technologies: Node.js, React Native, Apache Solr, Solr, Express.js, Sequelize

Developer | Contractor

2021 - 2021
US-based biotechnology company (via Toptal)
  • Created a desktop application, implementing a novel algorithm recently published by a collaborator. Worked as part of a team of scientists and engineers at a biotechnology startup.
  • Used Electron and Python to develop a production-ready, multiplatform desktop application based on research code written in MATLAB.
  • Developed production-level software for recognition, statistical analysis, and visualization of biological cell ensembles from a time series of microscopy images, using image processing techniques, particularly optical flow analysis.
Technologies: Electron, OpenCV, Computer Vision, Computer Vision Algorithms, Python, PyInstaller, MATLAB, NumPy

Developer (Consultant)

2016 - 2020
Partfiniti, Inc.
  • Provided technical guidance and facilitated the development transition of a web application that I had previously built for an outsourcing team.
  • Containerized the application using Docker and created automation using Ansible for bringing up deployment environments.
  • Undertook research and development to improve key product features.
  • Refactored an extensive legacy front-end codebase built on jQuery into a hierarchy of reusable components using React's 1-way data flow paradigm.
Technologies: Redis, RabbitMQ, React, Git, Composer, Phinx, Ubuntu, HTML, Apache Solr, Solr, Ansible, Docker, jQuery, JavaScript, MySQL, PHP 7, HTML5, SQL

Guest Researcher, Marie Curie ESR

2018 - 2019
Medical University of Vienna
  • Performed numerical simulations that shed light on the nature of phylogenetic quasi-terraces. Co-authored a paper:
  • Integrated a Terraphast library written in C into the popular phylogenetic package IQ-TREE. Acknowledged in the following paper:
  • Conducted numerical simulations and designed algorithms in the service of investigating phylogenetic terraces.
Technologies: Algorithms, Graphs, Data Visualization, SciPy, NumPy, Writing & Editing, Mathematics, Combinatorics, Bioinformatics, C, C++, Python, SQL

Lead Developer

2013 - 2016
Partfiniti, Inc.
  • Led the development of a greenfield SaaS ERP product to create a platform connecting fiber optics part manufacturers, vendors, and buyers.
  • Created a novel part configurator, bill of materials, and quoting tool that has since been used to quote products worth over $1,5 billion.
  • Invented and deployed a production implementation of a fiber optics part configurator. It qualitatively increased the product’s capabilities while lowering infrastructure costs. Patented as
  • Passed on the ongoing maintenance and operations of the product to an outsourcing company.
Technologies: Redis, RabbitMQ, Bootstrap, Ansible, Apache Solr, Solr, MySQL, Docker, PHP, Zend Framework, PHP 7, APIs, REST APIs, LinkedIn API, HTML5, Amazon Web Services (AWS), SQL

Lead Developer

2011 - 2012
JobRefer, Inc.
  • Joined as a front-end developer and took over the lead position at a San Francisco-based startup.
  • Built a small development team in Warsaw and led the development of B2B social recruiting web application.
  • Created a single-page application (SPA) front end for the web application.
Technologies: JSON, Ajax, PHP, PHP 5, CSS, HTML, JavaScript, Ext JS, HTML5, SQL

Web Developer

2009 - 2010
  • Maintained the legacy code and developed new features for internal and external projects.
  • Designed database schemas and developed an ORM-like collections library to supplement Zend Framework's database management features.
  • Gathered requirements from clients and non-technical team members.
Technologies: Zend Framework, PHP 5, jQuery, CSS, HTML, JavaScript, PHP, SQL

Web Developer

2008 - 2009
Hexlabs Ltd
  • Maintained and developed new features for the company’s flagship product,—an international real estate directory.
  • Maintained and developed new features for a complex customer relationship management (CRM) application.
  • Provided technical support for enterprise clients.
Technologies: MySQL, JavaScript, jQuery, Ext JS, T-SQL (Transact-SQL), Zend Framework, PHP, PHP 5, SQL

Weaver Dating
A React Native/Node.js dating mobile application for iOS and Android. I completed the whole project solo based on designs provided by the client. The back-end development included devising a matching algorithm based on Apache Solr.

A novel fiberoptics part configurator that sped up the process of identifying part numbers matching the user's requirements by an order of magnitude compared to existing solutions.

I designed the underlying algorithm, implemented and deployed a production version in the form of a web application integrated with a bill of materials (BOM) and quoting tools.

Patented as

Playlist Hunter

A React-based single-page application (SPA) that I developed for a Toptal client. I was the sole developer on this project, responsible for turning the client's overall idea into a concrete project by clarifying the business requirements, identifying optimal technology choices, full-stack implementation and deployment to production.

In addition to the core feature of allowing aspiring music producers to contact the relevant playlist curators, it can manage application feature subscriptions, calculate VAT, generate invoices, and has a GDPR-compliant control panel based on Laravel Voyager.

The back end is written in PHP on top of the Laravel framework and exposed to the front end as a REST API.

Admission Report
A fast SEO-optimized website that aggregates admission statistics of postgraduate and undergraduate degree programs in the United Kingdom. I conceived and developed this project on my own, growing it from zero to over 50,000 unique users (UU) per month.

Technically, it features an advanced pipeline for collecting, cleaning, and processing admissions information from many heterogeneous sources.
2018 - 2019

Doctor of Philosophy (Unfinished) in Molecular Biology | Bioinformatics

University of Vienna - Vienna, Austria

2016 - 2017

Master of Science (Distinction) in Astrophysics

Liverpool John Moores University - Astrophysics Research Institute, Liverpool, United Kingdom

2013 - 2015

Bachelor of Science (First Class Honors) in Applied Mathematics and Physics

The Open University - Milton Keynes, United Kingdom


PHP5 Zend Certified Engineer

Zend Technologies


jQuery, REST APIs, LinkedIn API, React, Node.js, Facebook API, X (formerly Twitter) API, Google Analytics API, NumPy, SciPy, Stripe, Stripe API, Vue, Python API, Laravel Voyager, OpenCV


Solr, Apache Solr, Ansible, Apache, FullStory, RabbitMQ, PhpStorm, Git, Composer, Ansible Tower, Stripe Checkout, GitHub, Webpack, NPM, Docker Compose, Jenkins, PyInstaller, MATLAB, Sequelize


Zend Framework, Laravel, Symfony, Ext JS, Bootstrap, React Native, Selenium, Electron, Express.js


PHP, PHP 5, PHP 7, JavaScript, HTML, HTML5, CSS, SQL, Python, C++, C, T-SQL (Transact-SQL), TypeScript


LAMP, Docker, Apache2, MacOS, Ubuntu, Amazon Web Services (AWS), Azure, Linode, Firebase, Heroku


MySQL, Databases, Redis, Phinx, MongoDB, Amazon S3 (AWS S3), JSON, Google Cloud


Search Engine Optimization (SEO), DevOps, Continuous Deployment, Unit Testing, Functional Testing

Industry Expertise



APIs, Web Scraping, Writing & Editing, Search Engines, Applied Mathematics, Mathematics, Computational Biology, Combinatorics, Physics, Computational Physics, Numerical Modeling, Numerical Simulations, Data Visualization, Graphs, Algorithms, Back-end, Architecture, Ajax, Cloudflare, Data Scraping, Responsive Web Apps, Single-page Applications (SPA), Google Play Store, Command-line Interface (CLI), Full-stack, General Relativity, Quantum Field Theory, Electrodynamics, Computer Vision, Computer Vision Algorithms

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