Сергій

Serhii Repchynskyi
Dnipro, Ukraine · [open contact info](look above in the "contact info" section) · [open contact info](look above in the "contact info" section)

Telegram · LinkedIn · Djinni · GitHub

Senior Backend Engineer · Python & Java

Backend engineer with 10+ years of experience building distributed systems, trading infrastructure, crypto

automation, and high-load real-time applications. Strong background in Java for game backends, centralized

exchanges, and HFT-style trading systems, with recent focus on Python for automation, Web3 integration, data

collection, and crypto tooling. Experienced with centralized and decentralized exchanges, low-latency

connectivity, Linux-based environments, and direct interaction with EVM and non-EVM blockchains through

Web3 and JSON-RPC tooling.

Summary

● 10+ years in backend engineering across fintech, gaming, crypto, and automation.

● Deep experience with trading systems, exchange connectivity, market data processing, and real-time

backend services.

● Strong hands-on work with Python automation, async data collectors, browser automation, and on-chain

integrations.

● Comfortable owning systems end to end: architecture, implementation, infrastructure, performance

tuning, and operational reliability.
Core Skills

Programming

● Python

● Java

● Go

● Solidity

● JavaScript

● SQL

Backend & APIs

● REST APIs

● WebSocket services

● Microservices-style architectures

● Real-time data processing

● JSON/CSV data pipelines

● Service integration and automation

Crypto & Trading

● Centralized and decentralized exchange integrations

● Spot, futures, and DEX market workflows

● Arbitrage and spread-trading infrastructure

● Latency-sensitive order routing

● On-chain monitoring and signal tracking

● Market and protocol event detection
Web3 & Blockchain

● EVM and non-EVM integrations

● Python Web3 and direct JSON-RPC interaction

● Contract calls, transfers, balances, and bridge workflows

● Log/event scanning and custom blockchain monitoring

● Trading- and campaign-related automation across multiple networks

Python Automation & Data Collection

● asyncio, aiohttp, WebSockets, multithreading, executor pools

● High-volume collectors and ingestion pipelines

● Browser automation with Playwright

● Low-level HTTP automation with custom sessions and proxy rotation

● Captcha handling, authenticated flows, and resilient retry logic

Databases & Infrastructure

● PostgreSQL, MySQL, SQLite

● Schema design, SQL optimization, joins, and aggregations

● Linux / Ubuntu administration

● Docker-based environments

● Networking, proxies, and backend operations

AI & Tooling

● AI-assisted development workflows

● LLM API integration for internal tools and automation

● Code analysis, refactoring, test generation, and rapid prototyping

● IntelliJ IDEA, PyCharm, JIRA, Git, SVN, Tomcat
Professional Experience

Python / Crypto Automation Engineer

Self-employed · Remote

2023 – Present

● Design and maintain Python-based automation for airdrops and retrohunting across multiple EVM and

non-EVM L1/L2 ecosystems, including wallet orchestration, faucet interaction, campaign workflows, and

on-chain/off-chain data collection.

● Build and operate services and pipelines that collect, normalize, and store high-volume market, trading,

and blockchain data in PostgreSQL, MySQL, SQLite, and file-based formats such as CSV and JSON.

● Develop automation that combines browser-level interaction through Playwright with direct HTTP and

RPC integrations, including proxy management, session handling, TLS fingerprinting, and

captcha-enabled flows where needed.

● Implement robust identity, wallet, and account-management layers with scheduled refresh, persistent

state, and failure-resistant retry strategies.

● Administer Linux-based infrastructure used for automation, data collection, and trading workloads,

including containers, services, and networking/proxy setups.
Senior Java Developer

Wildec · Dnipro, Ukraine

2011 – 2023

● Led backend and Android client development for the mobile game Pirates Fight, including real-time

multiplayer logic, matchmaking, and communication between Android clients and Java backend

services.

● Designed and implemented gameplay, networking, and server-side components for Wild Tanks Online,

with focus on responsiveness and stability under load.

● Built and maintained backend components for the centralized crypto exchange ShortBit, covering user

management, balances, order placement, matching flows, REST APIs, WebSockets, and market data

distribution.

● Developed automated high-frequency and arbitrage trading systems across major centralized exchanges

including Binance, Bybit, BitMEX, Gate.io, and OKX.

● Implemented automated trading strategies across decentralized exchanges such as Uniswap, SushiSwap,

PancakeSwap, and Balancer using off-chain services and Solidity components where needed.

● Collaborated with product, design, and operations stakeholders to deliver new features and improve

performance, reliability, and availability 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)

● Primary stack: Python, Linux, Web3 tooling; Java when project requirements justify it

● Domains: Trading systems, crypto infrastructure, automation, backend architecture, high-load services

● Interests: AI-driven tools, blockchain infrastructure, automation, performance optimization, algorithmic

trading, HFT