Sergiy Barlabanov, Developer in Friedberg, Germany
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Sergiy Barlabanov

Verified Expert  in Engineering

Software Developer

Friedberg, Germany
Toptal Member Since
August 4, 2021

Sergiy is a very passionate software engineer with 15+ years of experience in developing and operating software for a variety of businesses. He is capable of covering the full software lifecycle from requirements analysis and solution architecture to implementation and operation, from the front end to storage. Sergiy is a patient, ready-to-help team player with the evolved ability to teach, motivate, and inspire others.



Preferred Environment

Linux, MacOS, Java, Node.js, IntelliJ IDEA, Amazon Web Services (AWS), Azure, Docker

The most amazing...

...thing I've ever developed is a mammography software for the certification of radiology doctors. It was really challenging.

Work Experience

Software Developer, Technology Consultant

2009 - PRESENT
  • Designed and implemented core services and messaging architecture for a warehouse management system used in the biggest European warehouses (e.g., Adidas, Nestle, Transpharm, E.Leclerc, and Delhaize).
  • Designed, developed, and operated the GMX photo management web application serving 10,000+ users.
  • Set up an engineering team to develop an online B2B platform for public sector financing in Europe, led the development of the platform, and introduced and set up cloud-based infrastructure.
  • Accomplished a number of other projects in the last 10 years of my freelance career. Most of them are listed in the projects section.
Technologies: Amazon Web Services (AWS), Azure, Node.js, Java, Scala, Angular, Vue, Vuex, React, Apache Kafka, Kafka Streams, Akka, Elasticsearch, Spring, Spring Boot, TypeScript, JavaScript, Oracle, PostgreSQL

Software Engineer

2002 - 2008
Loyalty Partner GmbH
  • Designed and led the development of a software suite providing the framework and libraries necessary to implement loyalty management programs. The suite powers different international bonus systems (e.g., Lufthansa Miles and More and Payback Poland).
  • Helped coordinate, design, and implement critical parts of online transaction processing of Payback Germany.
  • Implemented critical parts of Deutsche BahnComfort, a bonus system of the German railway.
Technologies: Java, JavaScript

I helped to coordinate, design and implement critical parts of the online transaction processing of the Payback platform. Payback is a leading German bonus system with more than 30 million active users across the country.

SpamFreeWeb Ltd.

I co-founded and developed a nice and smart solution to protect Internet users against spam. It was a lot of fun. We had hundreds of active users in the friends and family phase, but the company failed to find an investor (it was during the crisis of 2008). But I am still proud of the software. I handled the development of browser plugins for IE and Firefox.

Loyalty Management Suite
I designed and led the development of a software suite providing framework and libraries necessary to implement loyalty management programs later used to power international bonus systems (e.g., Lufthansa Miles & More).

Warehouse Management System

I designed and implemented core services for a warehouse management system used in the biggest European warehouses (e.g., Adidas, Nestle, Transpharm, E.Leclerc, and Delhaize). I designed and implemented messaging architecture (100+ requests/second, latency < 60ms); redesigned a build pipeline for software with over 2 million lines of code; inspired, designed, and implemented an API for building complex warehouse layouts; and designed and developed an efficient Java NIO-based implementation of a binary protocol used to communicate with PLCs.

Torg UA

I co-founded and developed an e-procurement platform in Ukraine (1,000+ users), set up the engineering team, and led the development and operation of the platform. The platform implemented different bidding strategies and was highly concurrent.

Autoscout24 is Europe's leading online marketplace for new and used cars, bikes, and trucks. As a lead software engineer, I helped with the migration of an old .NET monolithic app to a cloud and Java stack. I developed and operated important parts of the platform (1+ million requests per minute); coached and trained team members; pioneered and evangelized reactive streams; inspired, promoted, and developed a stream-based architecture for data propagation across multiple services; and evangelized functional, reactive, and type-driven development.

B2B Platform for Public Sector Financing in Europe

Set up an engineering team to develop an online B2B platform for public sector financing in Europe, led the development of the platform, introduced and set up cloud-based infrastructure, set up continuous delivery pipelines, and set up and coordinated the agile development process (Kanban, trunk-based development, and feature toggles).

Document Management System for a Medical Government Institution

As a senior software engineer, I led the development of a document management system for a German medical government institution. I captured the requirements, prepared user stories, and designed and helped implement the features. The system was intended for internal use (200+ users) for clerks and call center employees.

Mammography Software for Certification of Radiology Doctors

Designed the architecture and implementation scenario for the migration of old client-server desktop-based mammography software to a software as a service platform. Implemented the prototype to demonstrate the main cornerstones of the new architecture. The software had to display and transform high-quality DICOM images in a browser.

GMX Photo Album
As a senior software engineer, I participated in the design and development of a GMX photo album (10,000+ users), an online photo management application for Germany's biggest email provider, GMX Mail. The application supported uploading, storage, transformation, and displaying images of different sizes and formats.

SaaS Platform for Energy Monitoring

I helped to plan, design, implement, and operate an energy monitoring platform for enterprise customers in Germany, Austria, and the Netherlands. The developed functionality included the collection and acquisition of telemetry data from multiple providers via REST and WebService APIs, MQTT brokers, Azure IoT Hubs, etc., storage of the corresponding time series, their normalization down- and upsampling, calculation of KPIs and derived time series, generation of reports, and anomaly detection and alarming.
1996 - 2002

Master's Degree in Computer Science

National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute" - Kyiv, Ukraine


Node.js, JMS, Vue, Vuex, React, Apache Lucene, Hibernate Search, JAX-RS, jQuery, Reactor, NgRx


IntelliJ IDEA, Kafka Streams, WildFly, ActiveMQ, Apache Maven, Ansible, Gradle, SBT, ImageJ, Citus, Azure IoT Hub, Auth0, Azure Kubernetes Service (AKS)


Hibernate, Spring, Angular, Spring Boot, JPA, Bootstrap, Play, JSON Web Tokens (JWT), Redux, Apache Wicket, Akka, ImageIO, Apache Camel


Java, JavaScript, HTML, Scala, TypeScript, GraphQL, C++, Ruby, Kotlin


Amazon Web Services (AWS), Azure, Docker, JEE, JBoss, Apache Kafka, Linux, MacOS, Oracle, Mule ESB, Kubernetes, JavaFX, Azure Functions


Elasticsearch, MongoDB, PostgreSQL, Microsoft SQL Server, Azure Cosmos DB


Hosting, Kanban, Azure DevOps


Software Engineering, WebLogic, GlassFish, CDI, Microsoft Azure, Project Reactor, DNS, Apollo Server, DICOM, Azure Service Bus, OAuth, Full-stack Development

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