Sergey Matsko

Backend Engineer (Python/FastAPI) — REST APIs, Microservices, LLM/RAG systems

Summary

Backend engineer with 7 years of Python experience building public-facing APIs and services for enterprise customers across telecom, metallurgy, FMCG and the public sector. I design and ship service architecture end to end — REST APIs, relational and vector data layers, streaming integrations, and deployment on Linux. Recently focused on LLM/RAG systems: built and shipped a retrieval pipeline with vector search (Milvus) end to end, from architecture to production. Comfortable owning a problem from design through review, tests and release, and experienced working in distributed teams across time zones. Currently open to full-time remote roles.

Favorite Python Packages:

FastAPI, SQLAlchemy, Pydantic, Django, Django REST Framework, Flask, pytest, LangChain, Alembic, httpx

Experience

Independent Contract Projects — Python Developer (Feb 2025 – Present, Remote)
B2B trading platform: extended the server side, built new backend modules and refactored legacy ones while keeping the public API contract stable.
Data analytics service (LLM-based): owned the architecture end to end and delivered it to production — FastAPI backend, Docker deployment on Ubuntu, data layer across PostgreSQL, MySQL, SQLite, ClickHouse and Milvus. Implemented similarity search over vector embeddings and the retrieval pipeline around it, and designed the database migration path.

Coding & Design LLC — Python Developer (Dec 2023 – Feb 2025, Remote)
Designed the architecture for services synchronizing user data between an HR system (1C), Keycloak and VK PeopleHub, with both bulk and API-driven sync. Designed RAG architectures, including an agent-based design and a retrieval stage on local models, for advertising moderation automation at a major telecom operator. Built a single configurable backend on a microservice architecture for a B2C promotional platform across 3 countries, integrating bank payment and mobile-money providers. Ran code review and mentored other backend developers.

EVAPPS — Python Developer (Jun 2021 – Dec 2023, Remote)
Built, from scratch, a camera-management service for a computer-vision pipeline at an industrial monitoring system (NLMK Group), plus the services integrating the ML layer with Kafka in both directions. Integrated a Bitcoin wallet with Bitcoin Core and ElectrumX for a P2P broker, added metrics collection and automated backups.

MegaFon — Developer (Aug 2019 – Jun 2021)
Built an integration service between HP Service Manager and third-party systems, including SAP HR over REST API. Implemented the authentication mechanism and wrote client libraries consumed by other teams

Skills

Backend Development, FastAPI