Rado Fulek, Developer in Midland Park, NJ, United States
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Rado Fulek

Verified Expert  in Engineering

Software Developer

Midland Park, NJ, United States
Toptal Member Since
July 28, 2021

Rado is a developer with versatile programming and problem-solving skills and four years of software development experience. Furthermore, he conducted cutting-edge research about graph algorithms and published 50+ research articles. His main strengths are in back-end development, but his diverse professional experience allows him to work efficiently on the front end. Rado's industry experience is backed by a bachelor's and master's degree in computer science and a PhD in mathematics.


Comity Inc
Kotlin, PostgreSQL, Dagger 2, Javalin, Git, AWS DevOps, IntelliJ IDEA...
University of California San Diego
Applied Mathematics, Calculus, Probability Theory, Combinatorics, Graph Theory...
Columbia University, IST Austria, University of Arizona
Computer Science, Applied Mathematics, Combinatorics, Python...




Preferred Environment

Visual Studio Code (VS Code), IntelliJ IDEA, Microsoft Visual Studio

The most amazing...

...thing I've done is discovering the first fast algorithm for the clustered planarity problem, which was open for 25 years.

Work Experience

Senior Back-end Developer

2021 - 2022
Comity Inc
  • Designed and implemented back-end service modules for a fintech app deployed to AWS based on Java and Kotlin, including integration and unit tests.
  • Built API clients and workflows for processing financial transactions based on the Plaid and Galileo API in the back end of a fintech app.
  • Executed automatic messaging infrastructure based on Courier API in the back end of a fintech app.
  • Created admin tools for a fintech app in Retool, allowing monitoring of events and managing and uploading documents.
  • Performed regular code reviews and actively participated in brainstorming sessions to identify product improvements.
  • Contributed to a Python module for extracting information from tax forms based on Amazon Textract.
Technologies: Kotlin, PostgreSQL, Dagger 2, Javalin, Git, AWS DevOps, IntelliJ IDEA, Ubuntu Linux, JavaScript, Retool, Plaid API, Gradle, Apache Maven, Software Engineering, Back-end Development, Web Development, Fintech, XML, Liquibase, REST APIs, Object-relational Mapping (ORM), Back-end, Linux, Amazon Web Services (AWS), Swagger, OpenAPI, APIs, REST, JSON Web Tokens (JWT), JSON, SMS, API Integration, Online Payments, Webhooks, Docker, Low Code, Low-code Development, Data Processing, Python, Debugging, User Interface (UI), Software Development, Plaid, Databases, OAuth 2, Integration Testing, Mockito, Ubuntu, JUnit, Java 11, GitOps, Web Security, Technical Writing, Technical Documentation, API Documentation, Integration, RESTful Services, Amazon Textract, MVP Design

Visiting Faculty

2020 - 2021
University of California San Diego
  • Taught online undergraduate-level courses on calculus, probability theory, and applied mathematics.
  • Organized guest lectures for students given by experts working in the industry.
  • Prepared study materials and pre-recorded lectures for online courses.
  • Published a research paper in the Symposium on Computational Geometry, the leading venue in computational geometry.
  • Managed teaching assistants who led discussion sessions in my classes and graded students' work.
Technologies: Applied Mathematics, Calculus, Probability Theory, Combinatorics, Graph Theory, Computational Geometry, Communication, Quantitative Analysis, Mathematics, LaTeX, Presentations, Microsoft Excel, Microsoft Word, PDF, 3D Math, Vectors, Geometry, Learning Management Systems (LMS), Bayesian Statistics, Statistics, Spreadsheets, Technical Writing, Writing & Editing

Research Fellow

2013 - 2020
Columbia University, IST Austria, University of Arizona
  • Resolved several long-standing open problems that withstood serious attacks from leading experts in computational geometry.
  • Improved the best-known quantitative estimates relaxing Conway's thrackle conjecture with a computer-assisted proof implemented in C++.
  • Confirmed experimentally the feasibility of a novel network visualization algorithm by its implementation in Python.
  • Created an educational application in Java, illustrating several phenomena pertaining to the geometric representation of graphs and circle packings.
  • Researched the connection between cascade and graphical models of influence spread over networks.
  • Published several research articles in the proceedings of leading venues on algorithms and computational geometry: ACM-SIAM Symposium on Discrete Algorithms (SODA) and Symposium on Computational Geometry (SoCG).
  • Invited to the program committee of the 24th, 26th, and 28th International Symposium on Graph Drawing and Network Visualization.
Technologies: Computer Science, Applied Mathematics, Combinatorics, Python, Combinatorial Optimization, Graph Theory, Computational Geometry, Algorithms, Communication, Software, Mathematics, Data Science, LaTeX, Geometry, 3D Math, Algebra, Quantitative Modeling, Data Pipelines, C++, Java, Presentations, Technical Writing, Writing & Editing, Machine Learning

Junior Developer

2004 - 2006
  • Implemented a substantial part of the initial release of the first flight reservation website in Slovakia, pelikan.sk, based on ASP.NET and mainly written in C#.
  • Built a desktop application as a user interface for a standalone database in Delphi with Object Pascal.
  • Implemented a substantial part of the initial release of slovakia.travel information portal based on ASP.NET and mainly written in C#.
Technologies: ASP.NET, Delphi, SQL, JavaScript, HTML, Object-oriented Programming (OOP), Software, Object Pascal, Software Engineering, Back-end Development, Web Development, C#.NET, .NET, Microsoft Visual Studio, C#, Windows, XML, Object-relational Mapping (ORM), Multithreading, Back-end, API Integration, Debugging, User Interface (UI), Relational Database Design, Software Development, Databases


iGraph is a popular C/C++ library for complex network analysis, emphasizing efficiency, portability, and ease of use.

I designed and integrated a module for generating triangulated meshes and their duals. Furthermore, I improved by order of magnitude the running time of implementing functionality for computing distances in graphs through a recently discovered heuristic and advanced optimization techniques.

Fintech App

A Kotlin-and-React-Native-based app facilitating payments of advance tax credits. I was primarily a back-end developer in charge of integrating payment providers, messaging infrastructure and implementing admin tools based on Retool.

Toptal React Academy

The Toptal React Academy is an exclusive learning program that teaches the React framework to selected members of the Toptal network. After a month of study, all graduates are tasked with completing a 30-40 hour final project to build and deliver a React app from scratch.

Angular Energy for Graph Visualizations

Designed and experimentally confirmed the feasibility of a novel network visualization algorithm using Python. The algorithm combines the technique of gradient descent and a novel notion of angular energy in drawings of networks.

Flight Reservation Web Application

Built the front end and back end for a flight reservation web application based on ASP.NET and Amadeus flight reservation system. The bulk of my work was integrating Amadeus with the rest of the booking engine.

Spring Embeddings and Circle Packings

Created an educational application in Java that illustrates several phenomena pertaining to geometric representation of graphs and circle packings. The application illustrates the interplay between the so-called spring embeddings of graphs and their representations by touching disks.

Atomic Embeddability, Clustered Planarity, and Thickenability

Resolved the clustered planarity problem that concerns a graph together with a hierarchical clustering on its vertices. This result has numerous immediate implications for algorithmic problems in the area of graph algorithms and has already inspired numerous follow-up research projects. The result was announced at the 2020 ACM-SIAM Symposium on Discrete Algorithms (SODA) and published by the highly respected Journal of the ACM.

YouTube Transcript Summarizer

Developed from scratch an extension to the Chrome browser that summarizes YouTube transcripts and provides a user-friendly GUI to adjust the parameters of the summary. The extension fetches video transcripts using URLs extracted from the HTML source and summarizes them by calling OpenAI API.


NetworkX is a popular Python library for studying graphs and networks. I improved the implementation of an algorithm finding an optimal traversal in a graph concerning edge weights and suggested further improvements for the performance.

Quinde Foundation

This project consisted of back-end development on Quinde's learning management system MVP.

In this project, I performed the following:
• Designed the back-end architecture and set up development and deployment infrastructures.
• Synchronized work between front-end and back-end developers.
• Implemented authentication and authorization functionalities.

Jogging API

REST API that tracks the jogging times of users.

I implemented it in Java SpringBoot with MySQL data tier.
I developed an advanced search functionality and integrated it with a third-party weather API. A reporting functionality supports PDF for average speed and distance per time period.
2008 - 2012

PhD in Mathematics

Swiss Federal Institute of Technology - Lausanne, Switzerland

2006 - 2008

Master's Degree in Computer Science

Simon Fraser University - Burnaby, BC, Canada

2000 - 2005

Bachelor's Degree in Computer Science

Comenius University - Bratislava, Slovakia

MARCH 2023 - MARCH 2026

AWS Solutions Architect Professional

Amazon Web Services


AWS Solutions Architect Associate

Amazon Web Services


AWS Certified Developer - Associate

Amazon Web Services


Toptal React Academy Graduate

Toptal, LLC


Node.js, React, Matplotlib, NumPy, REST APIs, SciPy, Pandas, Plaid API, Liquibase, OpenAPI, Asyncio, PySpark, Chai, Sinon.JS


LaTeX, IntelliJ IDEA, Spring Tool Suite (STS), Visual Studio .NET, Microsoft Visual C++, Jupyter, Git, Retool, Gradle, Apache Maven, Microsoft Visual Studio, Microsoft Excel, Microsoft Word, Spreadsheets, Plaid, Cloud Dataflow, GitHub, Amazon Cognito, Prism, Mongoose, Mocha, Amazon Textract


Python, Java, C#.NET, C, C++, Kotlin, SQL, Delphi, JavaScript, HTML, Object Pascal, C#, XML, PHP, Java Persistence Query Language (JPQL), CSS, Java 11, GraphQL, TypeScript


Amazon Web Services (AWS), AWS Lambda, Windows, Ubuntu Linux, Visual Studio Code (VS Code), Firebase, Linux, Docker, AWS Cloud Computing Services, Google Cloud Platform (GCP), Ubuntu, Amazon EC2, Cloud Native


Spring Boot, ASP.NET, Dagger 2, Javalin, Spring, .NET, Swagger, JPA, Hibernate, JSON Web Tokens (JWT), Flask, Django, Selenium, OAuth 2, Mockito, JUnit, AWS Serverless Application Model (AWS SAM), Express.js


Object-oriented Programming (OOP), Object-relational Mapping (ORM), Parallel Computing, Data Science, REST, Low-code Development, Serverless Architecture, Unit Testing, Microservices, DevOps


Databases, Relational Databases, MySQL, JSON, PostgreSQL, NoSQL, Amazon S3 (AWS S3), Amazon DynamoDB, Data Pipelines, Google Cloud, MongoDB

Industry Expertise

Network Security


Combinatorics, Graph Theory, Computational Geometry, Data Structures, Algorithms, Computer Science, Mathematics, Software Engineering, Back-end, Algebra, Combinatorial Optimization, Linear Algebra, Languages, Applied Mathematics, Probability Theory, University Teaching, Presentations, Communication, APIs, Software, Back-end Development, Matrix Algebra, Technical Writing, Writing & Editing, Technical Documentation, API Documentation, Computational Topology, Complexity Theory, Regular Expressions, Amadeus, Operations Research, Probabilistic Graphical Models, Neural Networks, Bayesian Inference & Modeling, AWS DevOps, Quantitative Analysis, Web Development, Fintech, Multithreading, Full-stack, SMS, Artificial Intelligence (AI), WebSockets, API Integration, Serverless, PDF, Online Payments, Webhooks, Front-end, Low Code, Data Processing, Debugging, Geometry, 3D Math, User Interface (UI), Learning Management Systems (LMS), Relational Database Design, CI/CD Pipelines, Quantitative Modeling, Software Development, Bayesian Statistics, Statistics, Cloud Services, Cloud Infrastructure, Cloud Architecture, Integration Testing, Chrome Extensions, OpenAI API, ES6 Promises, GitOps, Web Scraping, Amazon RDS, Amazon API Gateway, Web Security, Vectors, Calculus, AWS Cloud Architecture, Networking, Code Deployment, Codebase Development, Integration, RESTful Services, Architecture, OpenAI GPT-3 API, Cloud, GitHub Actions, Middleware, MVP Design, Machine Learning

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