Roman is available for hire

Roman Abakumov

Verified Expert in Engineering

Java Developer

Location

Kiev, Ukraine

Toptal Member Since

March 26, 2021

Roman is a Java developer with 15 years of experience developing a range of Java projects, including pure back-end services, desktop apps, and asynchronous back-end services using the reactive Play framework. He is proficient with the Spring framework family, has relational database expertise, and can create unit and integration tests for the code he delivers. Roman's area of expertise is building new integrations to the external services using REST/SOAP protocols

Back-end Debugging Windows Databases Java Spring Hibernate SQL Unit Testing Apache Maven Java Concurrency Agile Software Development PostgreSQL Git REST APIs Apache Wicket SBT

Portfolio

An Online Freelance Agency

Java, Databases, JavaScript, Spring Boot, MySQL, WebObjects, Project Lombok...

WorldTicket

Java, Spring Boot, JPA, REST APIs, RESTful Development, ETL, JDBC...

EPAM Systems

Play Framework, SBT, Liquibase, Spring Data, Reactive Programming...

Experience

Databases - 15 years Java - 15 years Spring - 15 years SQL - 15 years Apache Maven - 13 years Git - 8 years RESTful Development - 8 years REST APIs - 8 years

Availability

Part-time

Preferred Environment

Linux, Windows, Git, Apache Maven, Gradle, Java

The most amazing...

...thing I've made was the MyDHL solution that's in use all over the world. I also led the build of an ESG data collection system that analyzes environmental data.

Work Experience

Java Chief Software Architect

2018 - 2021

An Online Freelance Agency

Invented the tooling to automate team processes, output quality which was integrated with several data sources like Jira, GitHub, Google Sheets, and an external database; resulted in increasing the overall ticket quality and PR delivered by the team.
Investigated and fixed issues reported by customers/QA team and covered them with the unit and integration tests.
Majorly refactored various products for the sake of code maintainability, performance, and readability. The scope of refactorings was to get rid of dead and duplicated code, memory leaks, and long methods/classes.

Technologies: Java, Databases, JavaScript, Spring Boot, MySQL, WebObjects, Project Lombok, Spring Data, RESTful Development, REST APIs, Git, Spring, SQL, Apache Maven, PostgreSQL, Functional Programming, Hibernate, Unit Testing, Spring Security, Linux, Windows, Gradle, Ant Design, SOAP, HTML, Integration Testing, JSON, Microsoft SQL Server, jQuery, CSS, NPM, Kubernetes, XML, Java Concurrency, Jenkins, Back-end, Web Development, Amazon Web Services (AWS), REST, APIs, JEE, Software Architecture, Debugging

Product Lead | Architect

2017 - 2018

WorldTicket

Gathered all the requirements and dependencies to implement the airline operations dashboard, choose appropriate technology stack, and identify integration points.
Implemented the app's back end and implemented ETL to gather and transform the single-tenant databases to multi-tenant and transform the data to reporting format. The app returns data in a REST format and uses OAuth for authentication purposes.
Implemented a simple HTML/JavaScript-based UI; jQuery was used to operate with a DOM and Ajax used to fetch the data from the back end.

Technologies: Java, Spring Boot, JPA, REST APIs, RESTful Development, ETL, JDBC, Project Lombok, Apache Maven, Mercurial, Keycloak, Spring, Databases, SQL, Functional Programming, Unit Testing, Spring Security, Agile Software Development, JavaScript, Linux, Windows, HTML, Integration Testing, JSON, MySQL, Microsoft SQL Server, jQuery, CSS, Oracle, Jenkins, Bitbucket, Full-stack, Back-end, Web Development, REST, APIs, JEE, Software Architecture, Debugging

Senior Java Developer

2015 - 2017

EPAM Systems

Added new frameworks to increase the application functionality and make it easier to maintain such as the Integrated Java JSR 303 validation API.
Solved multiple optimization tasks to minimize the memory usage and latency of responses and also prevent resource leaks.
Optimized the SBT/Play configuration to minimize UT run time, minimize CI time, and reduce the development cycle length.

Technologies: Play Framework, SBT, Liquibase, Spring Data, Reactive Programming, Oracle Database, SQL, Java Concurrency, Git, Java, Spring, Databases, REST APIs, RESTful Development, Functional Programming, Hibernate, Unit Testing, Spring Security, Agile Software Development, Project Lombok, JasperReports, Linux, Windows, Integration Testing, JSON, Microsoft SQL Server, NPM, XML, Jenkins, Back-end, Web Development, REST, APIs, JEE, Software Architecture, Debugging

Senior Java Developer

2012 - 2015

EPAM Systems

Tailored eCommerce solutions to fit customer needs by developing all the missing functionality /extensions that were not provided out of the box.
Customized the build process to decrease build time by 4x without compromising on quality which helped to increase team output.
Led the team to resolve all the urgent client requests after production.

Technologies: SAP Hybris, eCommerce, Java, ImpEx, API Integration, Cockpit, Spring, Microsoft SQL Server, MySQL, SOAP, REST, SQL, Git, Databases, RESTful Development, REST APIs, Unit Testing, Spring Security, Agile Software Development, Project Lombok, JasperReports, Linux, Windows, Ant Design, Integration Testing, JSON, Java Concurrency, Jenkins, Back-end, Web Development, APIs, JEE, Software Architecture, Debugging

Product Lead | Senior Java Developer

2006 - 2012

Ciklum

Designed and implemented a new data model invented by the client and successfully launched it to production on time.
Managed the team to deliver the needed features on time while also maintaining quality and performance.
Implemented an export process to transfer a huge amount of data in a limited-service window and automized it to minimize human interactions.
Designed a batch-processing framework on the server part to run heavy load operations sequentially, monitor its execution, and control its lifecycle.
Communicated with a client to gather the requirements, translate them into technical tasks, and provided estimations.

Technologies: Hibernate, PostgreSQL, XML, Swing, JAXB, Ant Design, Apache Maven, Apache Wicket, RMI, jXLS, Big Data, SQL, Java, Spring, Databases, Git, Unit Testing, Spring Security, Agile Software Development, JasperReports, Linux, Windows, SOAP, Integration Testing, Microsoft SQL Server, Java Concurrency, Back-end, Web Development, APIs, Software Architecture, Debugging

Experience

MyDHL Global Website

https://mydhl.express.dhl/

A Play framework-based app which now in use all over the world to create and track shipments.

This application is highly customizable to be localized all over the world, including internationalization, and to follow all the rules and regulations in different countries about shipment processing.

Private users and organizations may use it, and even corporate users may build their own workflows around shipments.

This application was about to replace 13 legacy DHL portals and websites.

Airline Operational KPI Dashboard

This Spring Boot-based application gathers the data from multiple sources to the BI database and represents the most important information on the single screen. It uses ETL for data collection/transformation.

Jive Cloud

https://www.jivesoftware.com/

A Spring-based social networking app that is intended to be used for communication and collaboration solutions for business, including a suite of collaboration software and an intranet back end.

It supported a huge amount of integration to other collaborative systems.

ESG Data Collection and Transformation Software

The Spring-based software use Swing clients for data collection and complex workflows to transform, filter, and refine the data. The main users of this product were huge investment banks that use the data to refine their forecasts when making investments.

Canadian Tire ECOM Platform

https://www.canadiantire.ca/

An SAP Hybris ECOM solution developed for one of the biggest Canadian retailers.

I customized Hybris for the need of the customer to enable specific workflow and SKU management.

The Source Canada Initial Data Import

As part of the migration to the SAP Hybris, I handled the metadata and catalog import to the Hybris database from the old system. Later on, this data was used by the ECOM solution customized in further development.

Education

1997 - 2002

Bachelor's Degree in Computer Science

Donetsk State Institute of Artificial Intelligence - Donetsk, Ukraine

Skills

Libraries/APIs

REST APIs, JasperReports, jQuery, JDBC, Liquibase, JAXB, jXLS

Tools

Git, Apache Maven, Java Concurrency, SAP Hybris, SBT, Bitbucket, Gradle, Mercurial, NPM, Pentaho Data Integration (Kettle), Keycloak, Jenkins

Frameworks

Spring, Hibernate, Spring Boot, Swing, Ant Design, Play Framework, Spring Security, WebObjects, JPA, Apache Wicket

Languages

Java, SQL, XML, JavaScript, CSS, HTML

Paradigms

Agile Software Development, Functional Programming, Unit Testing, REST, RESTful Development, ETL, Reactive Programming

Platforms

Windows, JEE, Oracle Database, Docker, Oracle, Linux, Kubernetes, Amazon Web Services (AWS)

Storage

Databases, PostgreSQL, JSON, MySQL, Spring Data, Microsoft SQL Server

Other

Integration Testing, Project Lombok, Back-end, APIs, Software Architecture, Debugging, SOAP, Web Development, eCommerce, ImpEx, API Integration, Cockpit, RMI, Big Data, Full-stack

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