Hi, I'm Oleksandr Tkachenko

Full-Stack Developer

Results-driven Full-Stack Developer with 4+ years of experience building end-to-end web applications, from responsive React front ends to scalable Node.js, Python, and PHP (Symfony, CakePHP) backend services. Proven expertise across TypeScript, REST APIs, SQL, and major cloud platforms, with a track record of improving processing efficiency by 15% and ensuring 99.5%+ data accuracy for enterprise and U.S.-based projects.

About Me

I'm a results-driven Full-Stack Developer with 4+ years of experience designing and building end-to-end web applications — from responsive front ends to scalable backend services and cloud infrastructure. My journey began with a BSc in Data Science and Engineering from Kaunas University of Technology (KTU) in Lithuania, where I built a strong foundation in software architecture, databases, and parallel computing.

Throughout my career, I've worked on enterprise projects from Lithuania to Chicago, IL, building full-stack solutions that pair modern frontend frameworks like React with robust backend services in Node.js, Python, and PHP (Symfony, CakePHP). I combine this with strong data engineering fundamentals — SQL, ETL pipelines, and cloud platforms (AWS, GCP, Azure) — plus DevOps practices using Docker, Kubernetes, and Terraform to ship and operate reliable systems end to end.

My experience spans building customer-facing dashboards and APIs, architecting real-time data services, and modernizing legacy systems into cloud-native applications. I've also led freelance projects, delivering full-stack solutions — from the UI down to the database — that eliminated manual processes and gave clients self-service tools.

Full-Stack Web Applications
REST & GraphQL APIs
Cloud-Native Architecture

Technical Skills

Frontend Development

React TypeScript JavaScript (ES6+) Next.js HTML5 & CSS3 Redux

Backend Development

Node.js Express.js Python PHP Symfony CakePHP REST APIs GraphQL FastAPI

Databases

PostgreSQL MySQL MongoDB Redis SQL Server

Data Engineering

Apache Airflow Apache Spark Apache Kafka ETL/ELT Design Snowflake

Cloud & Infrastructure

AWS Google Cloud Azure Docker Kubernetes Terraform

DevOps & CI/CD

GitHub Actions GitLab CI Jenkins ArgoCD Git

Featured Projects

E-Commerce Analytics Pipeline

Architected a full-stack solution automating financial reporting and inventory management. Built a Python/PostgreSQL backend and reporting API that pulls daily sales from Shopify/PayPal, powering a Power BI dashboard and eliminating 20+ hours of monthly manual Excel work with report-ready data by 9 AM daily.

Python REST API PostgreSQL Shopify API Power BI

Legacy Database Modernization

Led migration of 50+ GB of operational data from legacy SQL Server to modern PostgreSQL with zero downtime, then rebuilt the legacy CakePHP application layer behind a customer analytics dashboard on Symfony — reducing report generation time from 2 minutes to under 15 seconds through query refactoring and API optimization.

PostgreSQL SQL Server Symfony CakePHP Python REST API Data Migration

Scalable Data Infrastructure - Project Roseland

Engineered full-stack data infrastructure — from backend pipelines to internal analytics APIs — supporting BI applications for a Chicago-based project. Reduced query costs by 15% through optimization, implemented real-time streaming with Kafka, and delivered the service layer powering dashboards at 99.5%+ data accuracy.

Snowflake Apache Kafka Apache Airflow Python Internal API

Multi-Client Data Integration Framework

Delivered reliable full-stack data infrastructure for 5+ clients across e-commerce, marketing, and professional services. Built a reusable Python service and lightweight monitoring dashboard for automated data quality checks, maintaining >99% accuracy and proactively surfacing discrepancies.

Python ETL Framework Dashboard Multi-Client

Professional Experience

Full-Stack Developer

Project Roseland, Chicago, IL 2022 - 2025
  • Engineered full-stack data infrastructure and internal APIs supporting analytics and BI applications for a U.S.-based project
  • Optimized data warehouse performance, reducing query costs by 15%
  • Implemented automated quality frameworks achieving 99.5%+ data accuracy
  • Built real-time streaming services with Apache Kafka, exposing high-velocity transactional data through internal APIs
  • Led migration from on-premise Hadoop to cloud-native services, including the application layer

Full-Stack Developer

Cogniteq, Vilnius, Lithuania 2020 - 2022
  • Built and optimized ETL pipelines and backend services for enterprise clients
  • Deployed change data capture (CDC) reducing reporting latency from 24 hours to 30 minutes
  • Developed reusable Python libraries and internal APIs accelerating pipeline development by 25%
  • Optimized Apache Spark jobs improving processing speeds by 35%

Full-Stack Developer

Emerline, Vilnius, Lithuania 2018 - 2020
  • Developed full-stack web applications in Symfony and CakePHP with a focus on DevOps practices
  • Containerized services using Docker and Kubernetes orchestration
  • Built CI/CD pipelines using Jenkins/GitLab CI
  • Managed AWS infrastructure with Terraform (IaC)

BSc Data Science and Engineering

Kaunas University of Technology (KTU) 2014 - 2018
  • Specialized in data engineering solutions and parallel computing
  • Key modules: Programming for Data Processing, Distributed Databases, Machine Learning

Let's Connect

I'm always interested in discussing data engineering challenges, new opportunities, or potential collaborations. Feel free to reach out!