Open to opportunities

Oskar Przegoń

@oskarprzego

Message

I build and test reliable API integrations, payments, and web applications.

Poland

Message

What I'm looking for

I'm looking to build and improve web or mobile products through API integrations, backend functionality, testing, and troubleshooting, while collaborating with stakeholders and growing across frontend and backend development.

I'm building 90 Days Challenge with a fitness coach, translating weekly discussions into product requirements, user flows, and implementation plans.

I implemented session-based authentication, onboarding, access control, and Przelewy24 payments with idempotent checkout, signed webhooks, provider verification, and concurrency-tested fulfillment. I also develop Fitti, an OpenAI API-powered chatbot for platform and workout questions.

I maintain 566 backend tests and 194 frontend Vitest tests across authentication, payments, APIs, and concurrent requests. At Hemmersbach, I built React views, validated forms, and admin tables integrated with REST APIs while resolving QA issues in a Scrum workflow.

My background also includes React Native mobile development, mining pool API integrations, Java, and client collaboration in English. I work across Next.js, FastAPI, PostgreSQL, testing, troubleshooting, and AI-assisted code review.

Experience

Work history, roles, and key accomplishments

Current

Company Website Developer

Current

SAP Climate (HVAC)

Jan 2026 - Present (7 months)

Based on the company's requirements, designed and implemented a responsive multi-page website using Next.js 14, TypeScript, and Tailwind CSS, with Framer Motion animations, mobile navigation, and SEO metadata.

Next.js TypeScript Tailwind Framer Motion SEO

Current

Co-Founder

Current

90 Days Challenge

Jan 2024 - Present (2 years 7 months)

Translate weekly discussions with the coach into requirements, user flows, and plans for subsequent implementation stages. Built session-based authentication, onboarding and access-control rules; integrated Przelewy24 with idempotent checkout, signed webhooks, provider verification and concurrency-tested fulfillment; continue to develop workout-session backend logic.

Next.js fastAPI PostgreSQL OpenAI API Przelewy24 Authentication Webhooks Testing Vitest Pytest

Frontend Developer Intern

Hemmersbach

Jul 2025 - Sep 2025 (2 months)

Built React views, forms with validation, and admin panel tables with pagination, filtering, and search; integrated them with REST APIs. Wrote unit tests, diagnosed and fixed issues reported by QA, and improved component rendering in a Scrum-based workflow using Git branches and pull requests.

React REST APIs Unit Testing Git Scrum

React / React Native Developer

Paidwork sp. z o.o.

Jan 2024 - Apr 2024 (3 months)

Communicated with English-speaking clients on project matters. Helped build a cryptocurrency-focused Android application from the ground up using React Native, while also working with Java code and integrations with mining pool APIs.

React Native Java Testing Debugging

React / React Native Developer Intern

Paidwork sp. z o.o.

Nov 2023 - Jan 2024 (2 months)

React Native Java Testing Debugging

React Native Developer Intern

Transition Technologies Software

Jun 2022 - Jul 2022 (1 month)

Co-developed a React Native fitness application as part of a team and participated in discussions with the client.

React Native

React Developer Intern

Kilfinnane Equestrian Web Development

Mar 2022 - Apr 2022 (1 month)

Built a website in React and collaborated with the client in English.

React

Junior Implementation Engineer

OSKAR PRZEGOŃ

Combines professional experience in React and React Native with hands-on work integrating REST APIs, testing, and developing solutions across frontend and backend.