About Mariia
Full-Stack Engineer with a focus on React, TypeScript, Node.js, and LLM integrations. I build production-grade web applications, AI-powered tools, and API infrastructure — from Chrome Extensions with active user communities to NestJS backends and RAG pipelines. I work AI-native: using LLMs as part of my daily development workflow, not as a novelty. Based in Warsaw, available for remote and on-site projects.
Recent projects include a dual-mode NestJS application with Docker Compose and MongoDB, an LLM proxy server with OpenAI-compatible API and real-time SSE streaming, a Telegram bot with async AI responses and D&D mechanics, and a Chrome Extension (MV3) with an active open-source community.
I'm comfortable working across the full stack — from architecting backend services and designing REST APIs to building responsive React UIs and integrating third-party APIs. I take security seriously: review code before running it, not after.
English
Fluent
Ukrainian
Native or bilingual
Russian
Native or bilingual
Can work on-site
Warsaw (up to 50km)
Experience
- Independent DeveloperFull-Stack Software EngineerDIGITAL AND ITFebruary 2024 - Today (2 years and 6 months)Warsaw, Poland
- LLM Proxy & API Infrastructure: Built a local proxy server (Node.js/Express/TypeScript) translating OpenAI-format requests to the Google GL API, featuring real-time SSE streaming, automatic token budget management, and a React dashboard with live telemetry.
- OpenAI-Compatible API Design: Designed and implemented a full request/response translation pipeline including system prompt injection workaround, context trimming, and streaming chunk re-wrapping — compatible with any OpenAI-format client.
- Offline-First SPAs: Shipped multiple production React 18/19 + TypeScript applications using Vite, Tailwind CSS, and Zustand, with responsive UIs, full i18n, localStorage persistence, GitHub Actions CI, and backup/restore pipelines
- Secure Browser-Side Code Execution: Engineered an iframe sandbox architecture with a MutationObserver pipeline, cross-origin postMessage communication, and ResizeObserver-based auto-sizing for safely rendering AI-generated content.
- Network Interception & Binary Manipulation: Developed a Tampermonkey userscript using window.fetch Proxy for auth token extraction, three-layer Supabase session reconstruction, raw PNG binary manipulation (tEXt chunk injection with CRC32 validation), and client-side ZIP generation.
- Chrome Extension (Manifest V3): maintain a browser extension serving an engaged open-source community, with rapid CI/CD release cycles managed via a Telegram feedback loop.
- Client-Side Data Pipeline: Designed a sanitization and chunking pipeline converting raw conversational data into structured, vector-ready JSON entries for LLM knowledge bases.
- NestJS Application with Dual-Mode Architecture: Built platform (NestJS/TypeScript + React 18 + MongoDB + Docker Compose) with dual-mode data layer — autonomous local seeding via batched PokeAPI sync with artificial rate-limit mitigation, switching to zero-external-request mode post-sync. Includes anti-tamper backend validation, persistent Docker volumes, and dual-layer input validation.
- FreelanceData Automation & Operations SpecialistJanuary 2020 - January 2023 (3 years)Built custom automation scripts for large-scale dataset processing with anomaly filtering and quality validation.Conducted end-to-end UAT and functional testing of digital tools and complex logic-flow routing prior to production deployment.Translated technical capabilities into actionable workflows for non-technical stakeholders, improving cross-team efficiency.
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Education
- C++ Programming & Data StructuresComputer Academy StepC++ Programming & Data Structures
- Cisco IT EssentialsCisco IT Essentials