Сергій

Serhii Repchynskyi
Dnipro, Ukraine · Phone: [open contact info](look above in the "contact info" section)
Email: [open contact info](look above in the "contact info" section)
Telegram: https://t.me/bizzzonnn
LinkedIn: [open contact info](look above in the "contact info" section)
Djinni: https://djinni.co/q/c1f23b8cba/

Senior Backend Engineer (Python / Java, Crypto & Trading)

SUMMARY
Senior Backend Engineer with 10+ years of experience in backend development and distributed systems,
specializing in trading, crypto, and high‑load real‑time applications. Strong background in Java (games, centralized
exchanges, HFT trading systems) and, in recent years, a primary focus on Python for automation,
airdrop/retrohunting infrastructure, Web3 integration, and crypto tooling. Experienced with both centralized and
decentralized exchanges, low‑latency trading connectivity, and direct interaction with EVM and non‑EVM blockchains
via Python Web3 and JSON‑RPC tooling for balances, transfers, bridges, contract calls, log/event scanning and other
tasks around arbitrage and on‑chain signal monitoring, all running on Linux‑based server environments.

CORE SKILLS
- Programming: Python, Java, Go, Solidity, JavaScript.
- Backend & APIs: RESTful APIs, WebSocket services, microservices‑style architectures, real‑time data processing,
JSON/CSV data pipelines.
- Crypto & Trading:
- Work with major centralized and decentralized exchanges (e.g. Binance, Bybit, OKX, Uniswap, PancakeSwap,
etc.) across spot, futures and DEX markets.
- Arbitrage, spread trading, latency‑sensitive order routing, basic frontrunning strategies, monitoring of on‑chain
events and “insider‑like” activities in the crypto ecosystem.
- Web3 & Blockchain:
- Integration and low‑level work with EVM and non‑EVM networks using Python Web3 and direct JSON‑RPC.
- Custom scanners and monitoring logic to detect arbitrage opportunities, liquidity movements, token listings and
protocol‑level events relevant to trading and campaigns.
- Python Automation & Data Collection:
- Asynchronous and concurrent collectors using asyncio, aiohttp, WebSockets, streaming HTTP, multithreading and
executor/thread pools to ingest and process high‑volume market, trading and on‑chain data into relational and
analytical storage, etc.
- End‑to‑end automation using both browser‑driven flows (Playwright with Chrome/Firefox‑based browsers) and
low‑level HTTP clients with custom TLS fingerprints, proxy rotation, authenticated sessions (cookies, headers,
tokens, signed requests) tailored to real‑world web applications and crypto campaigns, including solving captchas in
automated flows, etc.
- Data & Algorithms:
- Solid understanding of core data structures and algorithms, complexity analysis, and performance‑oriented design.
- Practical focus on building low‑latency, resource‑efficient components for trading and real‑time systems.
- AI & Tooling:
- Active use of modern AI tooling and LLM‑based assistants in daily development for code analysis, refactoring, test
generation, and rapid prototyping.
- Integration of AI/LLM APIs into internal tools and automation pipelines where it improves decision‑making,
monitoring, anomaly detection or data processing.
- Databases: PostgreSQL, MySQL, SQLite, SQL (schema design, performance tuning, complex joins and
aggregations).
- Linux & Infrastructure:
- Confident work with Linux/Ubuntu, DevOps‑style administration, services, Docker‑based environments, proxies
and other related tooling around backend and automation workloads.
- Tools & Ecosystem: IntelliJ IDEA, PyCharm, JIRA, Git (self-hosted), SVN, Tomcat, various Web3 and trading APIs.
PROFESSIONAL EXPERIENCE

Independent Python / Crypto Automation Engineer
Remote · 2024 – Present

- Design and maintain Python‑based automation for airdrops and retrohunting across multiple EVM and non‑EVM
L1/L2 ecosystems, including faucet interaction, wallet orchestration, on‑chain/off‑chain data collection and, in general,
interaction with campaign‑related activities and user journeys.
- Build and operate Python‑based services and data pipelines that collect, normalize and store high‑volume market,
trading and on‑chain data in PostgreSQL/MySQL/SQLite and file‑based storage (CSV/JSON) for further analytics and
decision‑making.
- Develop automation that combines browser‑level interaction (Playwright with Chrome/Firefox‑based browsers) and
direct HTTP/RPC calls, including proxy management, session and credential handling, TLS fingerprinting and
captcha solving where required, to reliably work with real‑world web applications and crypto projects.
- Implement robust session, identity and account‑management layers for large sets of wallets and accounts, including
scheduled refresh, state persistence and failure‑resistant retry logic.
- Administer and operate Linux‑based infrastructure used for trading, automation and data collection, using services,
containers (Docker), networking/proxy setups and other related tooling.

Senior Java Developer
Wildec · Dnipro, Ukraine · 2011 – 2024

- Led backend and Android client development for the mobile game “Pirates Fight”, including real‑time multiplayer
gameplay logic, matchmaking, and communication between Android clients and Java server backend.
- Designed and implemented core gameplay, networking, and server‑side components for “Wild Tanks Online”,
focusing on responsive real‑time interactions and stability of the backend under load.
- Built and maintained the backend of centralized (spot/futures) crypto exchange ShortBit using Java, Tomcat,
RESTful APIs, WebSockets, and MySQL, covering user management, balances, order placement, matching flows
and market data feeds.
- Developed automated high‑frequency trading systems for arbitrage trading between major centralized exchanges
(Binance, Bybit, BitMEX, Gate.io, OKX, etc.), including connectivity to REST/WebSocket APIs, order routing, spread
detection, monitoring and basic risk‑control mechanisms.
- Implemented automated high‑frequency trading strategies (arbitrage, basic frontrunning, cross‑DEX strategies)
across decentralized exchanges such as Uniswap, SushiSwap, PancakeSwap, Balancer on EVM and compatible
networks, using both off‑chain services and Solidity smart‑contract components where required.
- Collaborated with game designers, product and operations teams to deliver new features, optimize performance,
and ensure high availability and reliability of production systems.

EDUCATION

Dnipropetrovsk National University (DNU), Ukraine
- Master’s Degree, Applied Mathematics – “Automated Systems Software”, 2010 – 2011
- Specialist Degree, Applied Mathematics – “Intelligent Decision Systems”, 2009 – 2010
- Bachelor’s Degree, Applied Mathematics – “Intelligent Decision Systems”, 2005 – 2009

SoftServe IT Academy
- Java Development Program, 2011

ADDITIONAL INFORMATION

- Languages: Ukrainian (native), English (working proficiency; comfortable reading and using technical
documentation and specifications).
- Current primary tech stack: Python (backend, automation, trading tools), Linux, Web3 tooling; Java is used
optionally where it is technically justified or explicitly required by the project.
- Interests: AI‑driven technologies and narratives, blockchain infrastructure, automation, system performance
optimization, algorithmic trading, HFT, and the crypto industry in general.