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Mariusz Rakus
Verified Expert in Engineering
Software Developer
Mikołajki, Poland
Toptal member since February 18, 2026
Bio
Mariusz is a full-stack engineer with 8+ years of experience building production software for US-based startups and scale-ups. He specializes in TypeScript, React Native, Node.js, Python, and cloud infrastructure. Mariusz has delivered DirectDental’s React Native app, which contributed to its acquisition by Henry Schein (NASDAQ: HSIC) in 2025.
Portfolio
raqz.pl
TypeScript, Python, Supabase, OpenAI, Pgvector, FastAPI, Web Crawlers...
Inkitt Inc
React Native, Expo, TypeScript, React, NestJS, Node.js, Next.js, Tailwind CSS
STX Next
TypeScript, React Native, Node.js, FastAPI, Python, Expo, iOS, Android, Azure...
Experience
- TypeScript - 7 years
- PostgreSQL - 5 years
- Web Crawlers - 5 years
- Node.js - 5 years
- Bots - 4 years
- Azure - 3 years
- React Native - 3 years
- Python - 1 year
Preferred Environment
React Native, FastAPI, Node.js, PostgreSQL, Azure, React, LangChain, LangGraph, Firebase, Google Cloud
The most amazing...
...project I've led was the DirectDental's React Native app. It became the product that contributed to the company's acquisition by Henry Schein.
Work Experience
Senior Software Engineer
2019 - PRESENT
raqz.pl
- Architected and shipped a React Native field-sales app for a US pharma client, leading mobile + FastAPI/Azure back end across HIPAA-aware infrastructure and iOS distribution.
- Built and solo-shipped a React Native dental practice management app whose parent company was acquired by a NASDAQ-listed healthcare distributor (Henry Schein, HSIC) in 2025.
- Delivered production features for an a16z-backed Web3 wallet infrastructure startup (Dynamic.xyz), shipping Solana and EVM integrations consumed by hundreds of downstream applications.
Technologies: TypeScript, Python, Supabase, OpenAI, Pgvector, FastAPI, Web Crawlers, Embeddings from Language Models (ELMo), PostgreSQL, SQL, Telegram Bots, Discord Bots, WhatsApp, Bots, Event-driven Design (EDD), NestJS, Trigger.dev, Astro, React Native, Next.js, Retrieval-augmented Generation (RAG), Azure, Docker, Claude Code, AI Integration, AI Tools, Agentic Coding, Flask, Playwright, Bun, GitHub Actions, TanStack Router, Vite, Storybook, Resend, Artificial Intelligence (AI), Workflow Automation, APIs, Ollama, Cloudflare, BullMQ, Expo, Vercel, Webhooks, Internet of Things (IoT), Zoho Mail, OVH
Full-stack Mobile Engineer
2026 - 2026
Inkitt Inc
- Root-caused a +150% p50 Android app startup regression, audited 120+ million attestation requests, and eliminated ~470,000 failed integrity validations per week.
- Discovered and validated a critical unauthenticated account-takeover vulnerability in a web-app and designed the fix.
- Adapted an open-source engine into a Node.js emulator for device-free development, added QA automation, and mapped its back-end API surface.
Technologies: React Native, Expo, TypeScript, React, NestJS, Node.js, Next.js, Tailwind CSS
Lead Software Engineer
2026 - 2026
STX Next
- Worked as a staff-level senior full-stack engineer on an enterprise mobile application, owning end-to-end delivery across mobile architecture, a FastAPI and Python back end on Azure, iOS distribution, and cross-vendor compliance.
- Architected state management migration from Context API to Zustand, reducing render cycles on complex data grids. Migrated authentication from MSAL SDK to expo-auth-session with PKCE flow against Azure AD.
- Designed an end-to-end encrypted notes module (AES-256, PBKDF2 key derivation from PIN, and biometric unlock), meeting enterprise compliance requirements without server-side key access.
- Led iOS enterprise distribution combining Apple Developer Enterprise Program (ADEP) and Microsoft Intune MDM. Owned EAS Build CI/CD on Azure Pipelines, set up Detox and Maestro E2E tests, and integrated an AI assistant with a LangChain back end.
Technologies: TypeScript, React Native, Node.js, FastAPI, Python, Expo, iOS, Android, Azure, CI/CD Pipelines, Full-stack, React, PostgreSQL, Redis, CSS, HTML, LangChain, Next.js, Claude Code, Cursor AI, OpenAI, Claude, Tailwind CSS, AI Integration, API Integration, User Interface (UI), Responsive Web Design (RWD), Mobile UI, GitHub, UI Design, SQL, REST APIs, AI Tools, JavaScript, Bun, GitHub Actions, TanStack Router, Vite, Artificial Intelligence (AI), Workflow Automation, APIs, Cloudflare, Webhooks, LangGraph, LangSmith, WebSockets, Azure CLI
Senior Product Engineer
2021 - 2026
Sofomo
- Engineered full-stack SaaS products end-to-end for multiple US-based startups across healthcare, Web3, AI, and consumer verticals (DirectDental, Globality, PublicSQ, Willow, and Dynamic.xyz).
- Architected and shipped the DirectDental React Native mobile app from scratch, integrating with an existing Ruby on Rails API and contributing to the company’s 2025 acquisition by Henry Schein (Fortune 500, NASDAQ: HSIC).
- Built and maintained CI/CD pipelines (GitHub Actions and Azure DevOps), cutting release cycles and enabling continuous delivery across web and mobile platforms.
- Prototyped AI and RAG workflows and agentic automation tools using LangChain, OpenAI, and FastAPI, delivered as internal productivity and data-processing solutions.
Technologies: NestJS, Node.js, Express.js, Fastify, Next.js, React, React Native, Prisma, TypeScript, Python, FastAPI, PostgreSQL, Full-stack, Redis, CSS, HTML, iOS, Android, Ruby on Rails 6, Claude Code, Cursor AI, Slackbot, Tailwind CSS, Website Data Scraping, CI/CD Pipelines, AI Integration, API Integration, User Interface (UI), Web3, Responsive Web Design (RWD), Mobile UI, GitHub, UI Design, Amazon Web Services (AWS), Amazon S3 (AWS S3), SQL, REST APIs, Microservices, Slack, AI Tools, JavaScript, Playwright, Bun, GitHub Actions, TanStack Router, Vite, Storybook, Resend, Workflow Automation, APIs, Cloudflare, Expo, Bots, Vercel, Webhooks
Front-end Engineer (Web3)
2022 - 2023
Dynamic.xyz
- Built features for Dynamic.xyz, an a16z-backed Web3 onboarding and authentication platform for crypto wallets and dApps.
- Implemented front-end components and SDK integrations in TypeScript, React, and Next.js for a multi-chain wallet connection product.
- Collaborated with the Dynamic.xyz core team on UX and developer experience improvements for the embeddable widget and customer dashboards.
Technologies: TypeScript, React, Next.js, Web3, Full-stack, Node.js, PostgreSQL, Express.js, CSS, HTML, Tailwind CSS, API Integration, User Interface (UI), Responsive Web Design (RWD), Mobile UI, GitHub, SQL, REST APIs, Support & Maintenance, Prisma, EDA, JavaScript, APIs
Front-end Engineer
2021 - 2023
iRonin.IT
- Delivered front-end features for various US and EU clients of iRonin.IT, a software house specializing in JavaScript and Ruby on Rails projects.
- Worked with TypeScript, React, and Node.js across web applications and dashboards on a side-contract basis.
- Collaborated with distributed teams using Git, code reviews, and agile workflows to ship reliable production frontends.
Technologies: TypeScript, React, Node.js, CSS, HTML, Next.js, Tailwind CSS, CI/CD Pipelines, API Integration, User Interface (UI), Responsive Web Design (RWD), Mobile UI, GitHub, UI Design, JavaScript, APIs
Full-stack Developer
2020 - 2021
ITCraftship
- Built cross-platform mobile applications from scratch using Ionic and Angular, delivering iOS and Android releases from a single TypeScript codebase.
- Delivered production features in Flutter and Dart for a mobile client project.
- Built server-side rendered Next.js applications with optimized routing and data fetching strategies, improving initial page load and SEO indexing.
Technologies: Angular, Ionic, React, Next.js, TypeORM, Firebase, Firebase Realtime Database, Vue, Flutter, iOS, Node.js, Express.js, CSS, HTML, TypeScript, Android, Full-stack, Tailwind CSS, CI/CD Pipelines, API Integration, User Interface (UI), Responsive Web Design (RWD), Mobile UI, GitHub, UI Design, SQL, REST APIs, Microservices, Prisma, Website Data Scraping, JavaScript, Resend, APIs, Webhooks
Front-end Developer
2019 - 2020
SoftwareHut
- Built a Vue laboratory management interface for ORLEN Laboratorium, a unit of Poland's largest fuel and energy corporation, enabling lab technicians to track samples and analyses across multiple facilities.
- Developed a React-based gamification platform for GrowUperion, implementing point systems, leaderboards, and achievement tracking to drive employee engagement for corporate L&D programs.
- Migrated legacy JavaScript components to TypeScript across multiple client projects, introducing strict typing and reducing runtime errors during code reviews and QA cycles.
Technologies: React, Vue, TypeScript, Responsive Web Design (RWD), Node.js, CSS, HTML, Next.js, API Integration, User Interface (UI), Azure, Mobile UI, GitHub, UI Design, REST APIs, JavaScript, APIs
Front-end Engineer
2018 - 2020
Artneo
- Built and styled landing pages, marketing sites, and online shops for various small business clients of Artneo.
- Converted PDF and PSD designs into responsive HTML, CSS, and JavaScript-based web pages.
- Started a professional career in front-end development, learning version control, deployment, and client communication.
Technologies: HTML, JavaScript, React, CSS, TypeScript, API Integration, User Interface (UI), Responsive Web Design (RWD), Mobile UI, GitHub, UI Design
Experience
FSC Classifier
https://github.com/kolezka/fsc-classifierI built a RAG-based classifier that mapped companies and products to U.S. Federal Supply Class (FSC) codes used in DLA defense procurement. I crawled company websites and PDF capability statements using Puppeteer and Cheerio, parsed documents, and ran a hybrid pipeline with pgvector similarity search against previously classified companies as a long-term cache, with GPT-4o reranking and JSON-mode structured output as a fallback. I orchestrated asynchronous workflows using Trigger.dev with progress streaming to a Next.js front end. I built the system using NestJS, Prisma, PostgreSQL with pgvector, and OpenAI embeddings.
Telegram Spy
https://github.com/kolezka/tg-spy-publicA research platform I developed for the systematic collection and structured analysis of openly accessible activity on Telegram. Working across public and joinable groups and channels, it reconstructs membership and participation over time, models the relationships between participants, and progressively broadens its scope by following the references it encounters. The findings are presented through a web interface, a documented HTTP API, a conversational query bot, and a natural-language assistant.
Telegram Data Viewer
https://github.com/kolezka/tg-viewerAn OSINT toolkit for macOS — extracting, decrypting, and browsing Telegram data offline, including deleted messages and secret chats. It decrypts SQLCipher .tempkeyEncrypted databases and parses the Postbox binary format.
RentHunter
https://github.com/kolezka/renthunterRentHunter is a self-hosted rental-listing monitor for the Trójmiasto area. It crawls apartment offers from multiple portals, applies hard filters and optional AI scoring, and pushes a notification the moment an interesting offer appears. A Svelte SPA lets you search semantically, browse with sortable infinite scroll, inspect each offer's change history, watch the crawl in a live log console, and reconfigure everything live—all stored in PostgreSQL.
FlowBot
https://github.com/kolezka/flowbotI built a no-code automation platform for Telegram, Discord, and WhatsApp with 172+ node types and 386+ commits. I developed a visual workflow editor that enabled users to create complex, multi-step automations across messaging platforms without writing code. I implemented features such as flow chaining, variable interpolation, webhook integrations, conditional branching, scheduled triggers, and real-time message processing. I built the system as a TypeScript monorepo using Telegram MTProto (mtcute), the Discord Gateway, the WhatsApp Business API, a NestJS back end, a Next.js dashboard, PostgreSQL with Prisma, and Trigger.dev workers.
NL5H00X — Projector Firmware Reverse Engineering
https://github.com/kolezka/NL5H00XI reverse-engineered and customized the firmware of the NL5H00X consumer projector. I analyzed embedded Linux internals, dumped and repacked firmware images, identified service interfaces, and unlocked configuration paths not exposed by the stock UI. I published the project on GitHub as a reference for other owners of the same hardware family. I demonstrated low-level and embedded skills, including shell scripting, firmware analysis, binary tooling, and working with Linux on constrained devices.
Skills
Libraries/APIs
React, Node.js, REST APIs, Playwright, Vue, Drizzle, WebGL, OpenAI API
Tools
Expo, GitHub, Prisma, Claude Code, Slack, Claude, TanStack Router, Astro, DeepSeek
Languages
CSS, HTML, TypeScript, JavaScript, Python, SQL
Frameworks
React Native, Next.js, Tailwind CSS, NestJS, Express.js, Fastify, Ionic, Ruby on Rails 6, Angular, Flask, Flutter, LangGraph, Svelte
Paradigms
Responsive Web Design (RWD), UI Design, Microservices, Event-driven Design (EDD)
Platforms
iOS, Android, Vercel, Ollama, Firebase, Azure, Amazon Web Services (AWS), Docker, LangSmith
Storage
PostgreSQL, Firebase Realtime Database, OVH, Redis, Amazon S3 (AWS S3), Google Cloud
Other
CI/CD Pipelines, Mobile UI, APIs, Webhooks, Full-stack, Cursor AI, Slackbot, Trigger.dev, OpenAI, AI Tools, Website Data Scraping, AI Integration, API Integration, User Interface (UI), Web3, Cloudflare, TypeORM, Web Crawlers, Bun, GitHub Actions, Vite, Storybook, Resend, LangChain, EDA, BullMQ, FastAPI, Supabase, Support & Maintenance, Pgvector, Embeddings from Language Models (ELMo), Telegram Bots, Discord Bots, WhatsApp, Bots, Retrieval-augmented Generation (RAG), Agentic Coding, Workflow Automation, Artificial Intelligence (AI), Internet of Things (IoT), Zoho Mail, WebSockets, Azure CLI, Apprise, Open-source Intelligence (OSINT), Reverse Engineering, Data Encryption
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