Rado is available for hire

Rado Fulek

Verified Expert in Engineering

Software Developer

North Haledon, NJ, United States

Toptal member since July 28, 2021

Expertise

Mathematics Algorithms Back-end Developers Serverless Python AWS AWS Lambda Java Retool Node.js Software Development API LLM Plaid API AWS Textract Prism

Bio

Rado is a developer with versatile programming and problem-solving skills and six 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.

Portfolio

Ricoh Americas

CI/CD Pipelines, Amazon Web Services (AWS), Python, Event-driven Architecture...

Vayda

Retool, Python, FastAPI, React, PostGIS, PostgreSQL, TypeScript, JavaScript...

Comity Inc

Kotlin, PostgreSQL, Dagger 2, Javalin, Git, AWS DevOps, IntelliJ IDEA...

Experience

Data Structures - 8 years
Algorithms - 8 years
AWS Lambda - 3 years
Serverless - 3 years
Python - 3 years
Amazon Web Services (AWS) - 3 years
Large Language Model Operations (LLMOps) - 2 years
Retool - 2 years

Availability

Part-time

Preferred Environment

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

The most amazing...

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

Work Experience

Amazon Textract Developer

2023 - PRESENT

Ricoh Americas

Architected and implemented a scalable, available, and resilient event-driven document processing workflow designed to handle up to one million documents per day, and was adapted for several projects.
Built an automated ETL-based report generation of human reviewers’ performance.
Automated several tasks that were previously done manually related to document processing and report generation.
Increased the overall accuracy of AI-extracted data by at least 50%.
Devised a RAG-like algorithm to compute reliable confidence scores for LLM output.

Technologies: CI/CD Pipelines, Amazon Web Services (AWS), Python, Event-driven Architecture, NoSQL, Architecture, Technical Leadership, Agile, Solution Architecture, Amazon Textract, Retrieval-augmented Generation (RAG), Real-time Data, Software Architecture, Database Architecture, Large Language Models (LLMs), Data Architecture, HIPAA Compliance, Amazon EventBridge, Amazon Simple Queue Service (SQS), Natural Language Processing (NLP), AWS SDK, System Architecture, Optical Character Recognition (OCR), Large Language Model Operations (LLMOps)

Retool and Python Developer

2025 - 2025

Vayda

Migrated the admin dashboard from a React-based solution to Retool while improving its scalability and adding new search and report features.
Executed the heavy lifting of migrating a custom rich text editor from React to Retool.
Reverse-engineered the REST API calls functionality and redirected API calls in the custom rich text editor via Retool.

Technologies: Retool, Python, FastAPI, React, PostGIS, PostgreSQL, TypeScript, JavaScript, HTML

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 the 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, Minimum Viable Product (MVP), Finance APIs, Finance, Financial Modeling, Optical Character Recognition (OCR), Natural Language Processing (NLP)

Visiting Faculty | E-learning Developer

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 | E-learning Consultant

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, Education, Mathematical Modeling, Monte Carlo Simulations, Monte Carlo, Forecasting

Junior Developer

2004 - 2006

ISOMI

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

Experience

iGraph

https://github.com/igraph

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 the running time of a computation of distances in graphs by an order of magnitude through recently discovered heuristics 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

https://github.com/rfulekjames/restaurant

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

https://en.wikipedia.org/wiki/Clustered_planarity

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 several 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

https://github.com/rfulekjames/youtube-transcripts-summary

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

https://networkx.org/

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

Quinde Foundation

https://quinde.org/

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

I designed the back-end architecture and set up development and deployment infrastructures. I also synchronized work between front-end and back-end developers, implementing 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.

Loca11y

https://www.loca11y.org/

I worked as a back-end developer on the project, contributing a substantial portion of the back-end codebase and infrastructure setup. I designed back-end tests and integrated them with GitHub Actions. I also brainstormed the architecture and its improvements.

Real-time API for Hummingbot

Built an HTTP API to allow real-time interaction with the Hummingbot open-source cryptocurrency trading framework. The endpoints allowed instant updating of trading strategies, which otherwise was not available.

Education

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

Certifications

MARCH 2023 - MARCH 2026

AWS Certified Solutions Architect – Professional

Amazon Web Services

DECEMBER 2022 - DECEMBER 2025

AWS Certified Solutions Architect – Associate

Amazon Web Services

SEPTEMBER 2022 - SEPTEMBER 2025

AWS Certified Developer – Associate

Amazon Web Services

OCTOBER 2021 - PRESENT

Toptal React Academy Graduate

Toptal, LLC

Skills

Libraries/APIs

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

Tools

Retool, LaTeX, IntelliJ IDEA, Spring Tool Suite (STS), Visual Studio .NET, Microsoft Visual C++, Jupyter, Git, Gradle, Apache Maven, Microsoft Visual Studio, Microsoft Excel, Microsoft Word, Spreadsheets, Plaid, Cloud Dataflow, GitHub, Amazon Cognito, Prism, Mongoose, Mocha, Amazon Textract, AWS Cloud Development Kit (CDK), Amazon SageMaker, Amazon Simple Queue Service (SQS), Amazon Simple Notification Service (SNS), AWS CloudFormation, AWS CodeDeploy, AWS CodeBuild, Terraform, AWS SDK

Languages

Python, Java, Python 3, C#.NET, C, C++, Kotlin, SQL, Delphi, JavaScript, HTML, Object Pascal, C#, XML, PHP, Java Persistence Query Language (JPQL), CSS, Java 11, GraphQL, TypeScript

Paradigms

Event-driven Architecture, Object-oriented Programming (OOP), Object-relational Mapping (ORM), Agile, Parallel Computing, REST, Low-code Development, Serverless Architecture, Unit Testing, Microservices, DevOps, HIPAA Compliance

Platforms

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, Hummingbot

Storage

Databases, Relational Databases, MySQL, JSON, PostgreSQL, NoSQL, Amazon S3 (AWS S3), Amazon DynamoDB, Data Pipelines, Google Cloud, MongoDB, Azure SQL, Azure SQL Databases, Database Architecture, PostGIS

Frameworks

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 (SAM), Express.js

Industry Expertise

E-learning

Other

Combinatorics, Graph Theory, Computational Geometry, Data Structures, Algorithms, Computer Science, Mathematics, Software Engineering, Back-end, Serverless, Algebra, Software Architecture, Solution Architecture, Optical Character Recognition (OCR), Large Language Model Operations (LLMOps), Combinatorial Optimization, Linear Algebra, Languages, Applied Mathematics, Probability Theory, University Teaching, Presentations, Communication, APIs, Software, Back-end Development, Matrix Algebra, Technical Writing, Writing & Editing, Network Security, Technical Documentation, API Documentation, Technical Leadership, Real-time Data, Large Language Models (LLMs), Computational Topology, Complexity Theory, Regular Expressions, Amadeus, Operations Research, Probabilistic Graphical Models, Neural Networks, Bayesian Inference & Modeling, AWS DevOps, Quantitative Analysis, Data Science, Web Development, Fintech, Multithreading, Full-stack, SMS, Artificial Intelligence (AI), WebSockets, API Integration, 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, 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, Amazon Bedrock, Amazon Comprehend, AWS CodePipeline, Retrieval-augmented Generation (RAG), Education, Data Architecture, Mathematical Modeling, Monte Carlo Simulations, Monte Carlo, Forecasting, Minimum Viable Product (MVP), Finance APIs, Finance, Amazon EventBridge, Natural Language Processing (NLP), System Architecture, Financial Modeling, Algorithmic Trading, FastAPI

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