Олег

Oleh Voloshyn
Backend Developer (Node.js / TypeScript)

Phone: [відкрити контакти](див. вище в блоці «контактна інформація») | Email: [відкрити контакти](див. вище в блоці «контактна інформація»)

GitHub: https://github.com/Sledgeee

PROFESSIONAL SUMMARY

Backend Developer with 3+ years of commercial experience building scalable REST
APIs, e-commerce platforms and SaaS systems. Strong expertise in Node.js,
TypeScript, PostgreSQL and distributed systems. Experienced in payment
integrations, webhook-driven architecture, caching strategies and microservices.
Focused on clean architecture, performance optimization and production-ready
solutions.

TECH STACK

Languages: TypeScript, JavaScript

Backend: Node.js, NestJS, Express.js

Databases: PostgreSQL, Redis, MongoDB

Messaging: RabbitMQ

DevOps: Docker, NGINX

Other: REST API, Microservices, Webhooks, Payment Integrations, Caching

COMMERCIAL EXPERIENCE

Backend Developer (Freelance) | 2023 – Present

• Designed and developed scalable REST APIs using NestJS and Express.
• Integrated payment systems (Stripe, LiqPay) including webhook-based billing
logic and transaction handling.
• Designed relational database schemas and optimized complex PostgreSQL
queries.
• Implemented Redis caching strategies to improve performance and reduce
database load.
• Developed SRM/CRM systems (under NDA) with role-based access control and
reporting modules.
• Built asynchronous processing flows using RabbitMQ.
• Configured Dockerized environments and NGINX reverse proxy for production
deployments.
• Collaborated with frontend teams (Next.js) to deliver full-stack solutions.

SELECTED PROJECTS

SmartSelect – E-commerce Platform

• Built with NestJS (backend) and Next.js (frontend).
• Designed PostgreSQL schema with indexing and relational integrity.
• Integrated LiqPay payment gateway with secure transaction validation.
• Implemented Redis caching for product catalog and session handling.
• Developed admin dashboard with product, order and user management.
• Ensured API security using JWT authentication and role-based access.

LuminaLight – E-commerce System

• Developed scalable backend architecture using NestJS.
• Implemented product filtering, pagination and search optimization.
• Optimized PostgreSQL queries to improve response time.
• Implemented order processing logic and business validation rules.
• Integrated Redis for caching frequently requested data.

UaTube – Microservices Video Platform (Bachelor Thesis)

• Designed microservices architecture using NestJS.
• Used PostgreSQL and MongoDB for structured and unstructured data.
• Implemented RabbitMQ for inter-service communication.
• Integrated Meilisearch for fast video search functionality.
• Implemented video processing pipeline using FFmpeg.
• Designed authentication system and scalable API gateway layer.

DIVI TV – Subscription Video Platform

• Designed and implemented subscription-based backend architecture.
• Integrated Stripe for one-time payments and recurring billing.
• Implemented webhook-driven subscription lifecycle handling (activation,
renewal, cancellation).
• Designed relational PostgreSQL schema for users, subscriptions and access
control.
• Implemented JWT authentication and role-based authorization.
• Configured NGINX reverse proxy and production deployment.
• Optimized database queries and caching layer using Redis.

Moneywave CRM – Internal Financial CRM System

• Developed modular backend architecture for CRM system.
• Designed PostgreSQL schema with complex relations (users, leads, transactions,
statuses).
• Implemented role-based access control (RBAC).
• Built reporting endpoints with filtering, pagination and aggregation queries.
• Implemented Redis caching for dashboard statistics.
• Containerized services using Docker.

Finance CRM + Trading Platform

• Designed backend for trading-oriented CRM system.
• Implemented real-time data updates using WebSockets.
• Developed transaction and balance tracking logic.
• Built secure financial operations layer with validation and atomic DB
transactions.
• Implemented activity logging and audit trails.
• Optimized high-frequency query execution using indexes and caching.

Flowscore – Sports Data & Analytics Platform

• Integrated third-party sports data APIs.
• Built REST API layer for match data, statistics and team information.
• Implemented proxy architecture to normalize external API responses.
• Designed scalable data models for sports events.
• Implemented caching layer to reduce third-party API calls.
• Structured project for future analytics and AI-driven extensions.

NutrimateAI – AI-Powered Nutrition & Recommendation Platform

• Designed backend architecture for AI-driven nutrition recommendation system.
• Integrated AI APIs (LLM-based recommendation engine) for generating
personalized meal plans.
• Implemented user profile logic including dietary preferences, calorie goals and
restrictions.
• Designed relational PostgreSQL schema for users, plans, history and analytics.
• Built REST API for meal generation, plan updates and tracking.
• Developed token usage tracking and rate-limiting mechanisms.
EDUCATION

Khmelnytskyi National University – Bachelor in Computer Engineering (2020 –
2024)

Khmelnytskyi National University – Master in Information Systems and
Technologies (2024 – 2025)

LANGUAGES

Ukrainian – Native

English – Intermediate