Igor Khromov, Developer in Warsaw, Poland
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Igor Khromov

Verified Expert  in Engineering

Full-stack Java Developer

Warsaw, Poland
Toptal Member Since
April 21, 2014

Igor is a senior Java developer with experience in enterprise back-end development. He specializes in eCommerce, marketplaces, e-learning, NLP, travel, and finance. He has also received a master's degree in computer science and passed Oracle Java certification. Igor is a reliable and responsible individual who has been working remotely in the US and European markets for the last nine years.


Menai Group
Java 8, Docker, Redis, NATS, MariaDB, Amazon Web Services (AWS), TimescaleDB...
Toptal Enterprise Customer (NDA)
Google Cloud, Apache Kafka, Akka, Akka Streams, Kubernetes...
Toptal Customer (NDA)
Amazon Web Services (AWS), Redux, Amazon S3 (AWS S3), PostgreSQL, Spring, React...




Preferred Environment

MacOS, Sublime Text, DataGrip, IDEA IDE, Linux, Unix, Terminal, Shell Commands, Bash Script

The most amazing...

...thing I've done is the design of microservices that reduced the cost of developing new changes by 80%.

Work Experience

Senior Java Developer

2022 - 2022
Menai Group
  • Developed and supported microservices as part of a big trading system.
  • Wrote dozens of client libraries to interact with financial data API (crypto exchanges, financial statistics API, banks, etc.).
  • Made system integrations based on NATS subjects/streams.
  • Created clients to access microservice REST APIs easily.
  • Wrote tens unit and functional tests to cover most of the service functionalities.
  • Refactored lots of old code to have a solid and supportable codebase.
Technologies: Java 8, Docker, Redis, NATS, MariaDB, Amazon Web Services (AWS), TimescaleDB, PostgreSQL, Apache Maven, Git

Principal Java Developer (via Toptal)

2021 - 2021
Toptal Enterprise Customer (NDA)
  • Designed and developed SpringBoot microservice on Hexagonal Architecture hosted in Google Cloud.
  • Implemented Akka Stream flows for processing Kafka messages.
  • Helped to create a deployment flow with Harness and Google Cloud (GKE).
  • Wrote unit tests and integration tests with Testcontainers.
  • Made service configurations to enable tracing with Opentelemetry and New Relic as a vendor.
Technologies: Google Cloud, Apache Kafka, Akka, Akka Streams, Kubernetes, Google Kubernetes Engine (GKE), OpenTelemetry, New Relic, Java, CQRS, Hexagonal Architecture, Test-driven Development (TDD), Agile Software Development, SQL, Jira, MacOS, IDEA IDE, Apache Maven

Senior React and Java Full-stack Developer (via Toptal)

2020 - 2021
Toptal Customer (NDA)
  • Designed a database schema for a project management system.
  • Designed and implemented REST services with Spring MVC and Spring Security (RBAC) for a client's React app.
  • Planned and built a client's UI application with React and Redux.
Technologies: Amazon Web Services (AWS), Redux, Amazon S3 (AWS S3), PostgreSQL, Spring, React, JavaScript, Java, REST APIs, Amazon EC2, Amazon Simple Email Service (SES), Redis, Amazon API, Scrum, Agile Software Development, SQL, Jira, MacOS, IDEA IDE

Senior Java Developer | Team Lead | Tech Lead

2018 - 2021
  • Developed microservices with Spring Boot, RabbitMQ, Redis, and MongoDB.
  • Solved problems involving old-style architecture, moving them to a new level.
  • Created a list of Bash Scripts to automate the development environment and reduce delivery time.
  • Utilized Linux terminal sessions, session managers, terminal commands, Docker, and Docker Compose.
  • Created load tests with Selenium for testing different execution paths.
  • Developed integration and end-to-end tests to test microservice integrations.
  • Interviewed new team members, backlog management, junior or middle-level members mentoring.
Technologies: Amazon Web Services (AWS), Gradle, Apache Tomcat, SOAP, REST, Spring, PostgreSQL, Oracle, Redis, Docker, RabbitMQ, Java, REST APIs, Kubernetes, Technical Leadership, Amazon EC2, Amazon Simple Email Service (SES), Amazon API, Elasticsearch, Test-driven Development (TDD), Scrum, Agile Software Development, SQL, Jira, CentOS, Kanban, MacOS, IDEA IDE

Senior Java Developer | Tech Lead | CTO

2015 - 2018
  • Designed and developed back-end and mobile architecture solutions.
  • Designed and developed an SQLite database schema and migration module.
  • Designed and developed an Android application with specific requirements for performance.
  • Developed an NLP analytics module to parse publicly available datasets.
  • Set up the development, QA, and production environments for CI/CD.
  • Helped the team to integrate advertisement and analytics solutions.
  • Designed and developed a module for cross-platform mobile subscriptions for iOS and Android.
  • Developed a website admin panel as a single-page application.
Technologies: Amazon Web Services (AWS), NGINX, Apache Tomcat, Git, Android, PostgreSQL, Natural Language Processing (NLP), Generative Pre-trained Transformers (GPT), Gradle, Apache Maven, Hibernate, Spring, Java, REST APIs, Technical Leadership, Amazon EC2, Amazon Simple Email Service (SES), TypeScript, Flexbox, Redis, FreeBSD, Amazon API, Elasticsearch, Test-driven Development (TDD), Scrum, Agile Software Development, SQL, Jira, CentOS, Kanban, MacOS, IDEA IDE

Back-end Developer (Remote)

2014 - 2015
Sell It App
  • Designed and developed an API for a geospatial search within a certain radius.
  • Designed and developed a RESTful API for mobile and web platforms.
  • Developed an image storage service based on Amazon S3.
  • Helped to install and set up pipelines for unit and integration tests run on CI.
  • Integrated Openfire XMPP Server to a server-side app for real-time chats in mobile applications.
  • Wrote a module for API testing under high-load operations.
  • Helped stakeholders create user stories with detailed requirements for a dev team.
Technologies: Amazon Web Services (AWS), Apache Tomcat, NGINX, Git, PostgreSQL, MySQL, Openfire, Jenkins, Apache Maven, Hibernate, Spring, Java, REST APIs, Technical Leadership, Amazon EC2, Amazon Simple Email Service (SES), Redis, Amazon API, Agile Software Development, SQL, Jira, MacOS, IDEA IDE

Back-end Developer

2014 - 2015
  • Developed services and modules on the back-end for a news platform.
  • Integrated a third-party API for advertisement and log-in.
  • Worked closely with product owners and the marketing team to create detailed requirements.
  • Fixed website performance issues with database queries.
  • Developed a responsive markup to fit the most-used phone, tablet, and desktop resolutions.
Technologies: Amazon Web Services (AWS), TeamCity, NGINX, Subversion (SVN), MySQL, JavaScript, Java, REST APIs, Technical Leadership, Agile Software Development, SQL, Jira, MacOS, IDEA IDE

Global enterprise hotel, flight and rental car corporation (via Toptal)

Online travel agency for finding discount rates for travel-related purchases such as airline tickets and hotel stays. The company facilitates the provision of travel services from its suppliers to its clients.

• Develop microservice with Spring Boot built on hexagonal architecture.
• Create an Akka Stream pipeline to consume, process, and produce Apache Kafka messages.
• Create logging, tracing, metrics configs to integrate with NewRelic.
• Write unit integration tests to cover the most important parts of application logic.

Critical Event Communication System

Developed a critical event management communication system using emails, SMS, telephone calls, faxes, pager messages, and more. As one of the largest and most reliable critical communications providers in the world, the company combines artificial intelligence (AI), machine learning, unmatched expertise, and a modern platform.

• apply requirement developed by US Government for Securing Cloud Services (FedRAMP);
• Split big monolithic applications to microservices.
• Create microservice integrations with queues, files, DBs.
• Create deployment flow with Docker and Kubernetes.
• Create Selenium tests.
• Create unit tests.
• Create integration tests with Testcontainers.
• interviewed new team members, junior or middle-level members mentoring.
• Backlog management.

Project Management System (via Toptal)

A single-page web application for project management that allows users to create projects and tasks, upload files, and write comments on tasks.

• Design and develop SpringBoot RESTful API for Web UI application.
• Design and develop a security application layer with Spring Security and Redis as session storage.
• Integrate services with AWS S3 to download and upload files on Web UI and share objects with a presigned URL;
• Create unit and integration tests to cover the most important application functionality.
• Create Docker images to deploy with docker-compose on local and remote environments.
• Design database schema for PostgreSQL.
• Create DB migration process using Liquibase to safely evolve database schema.

SpringBoot RESTful Web Service for mobile applications with NLP

REST API for a mobile application that allowed students to improve English language skills by extending the language dictionary.

• Register and log in with Email, Google Auth, Facebook Auth.
• Token-based authorization with Redis as session storage.
• RBAC with Spring security.
• User profile management.
• Cross-platform user subscriptions on iOS, Android, and web.
• Database schema and migrations.
• Build statistical service tools to analyze big text datasets using Natural Language Processing (NLP) libraries.

SpringBoot RESTful Services for eCommerce Mobile and Web Applications

Provider of an e-commerce platform for local goods. The company develops an online platform that offers digital.

• Lead a team of six people.
• Interview and hire developers for the globally distributed team.
• Develop SpringBoot RESTful service for a mobile application as a client.
• Develop SpringBoot RESTful service for Web admin page for goods management, specifically the approval process.
• Install and support clustered Openfire XMPP jabber server as a chat server for mobile iOS and Android mobile applications.
• Create a custom plugin for Openfire to store chat history in PostgreSQL.
• Create CI/CD with Jenkins.

Enterprise News Platform

International art market around the clock with daily art world news, expert commentary, and event reviews.

• Extend existing system with new features and functionality.
• Profile and fix bottlenecks with slow code, SQL executions.
• Develop new monolith modules.
• Manage three team members.
• resolve build system dependency conflicts;
• follow best practices in responsive UI development for phone, tablet, and desktop screens support.
2002 - 2007

Master's Degree in Software Engineering of Automated Systems

Kharkov University of Air Forces - Kharkov, Ukraine


Oracle Certified Associate, Java SE 8 Programmer



REST APIs, Flexbox, Amazon API, Liquibase, React, Akka Streams


IDEA IDE, Sublime Text, Amazon Simple Email Service (SES), Git, Jira, NGINX, TeamCity, DataGrip, Terminal, Apache Maven, Jenkins, Apache Tomcat, Gradle, RabbitMQ, Subversion (SVN), Google Kubernetes Engine (GKE)


Spring, Redux, Spring MVC, Spring Boot, Spring 5, Hibernate, Spring JDBC, Akka, Spring Security, Apache Spark


Microservices, Kanban, Agile Software Development, Scrum, Test-driven Development (TDD), REST, CQRS


Java, JavaScript, TypeScript, SQL, Java 8, Bash Script


PostgreSQL, MySQL, Amazon S3 (AWS S3), Elasticsearch, MongoDB, Redis, Google Cloud, MariaDB


Docker, Amazon EC2, Amazon Web Services (AWS), MacOS, CentOS, Unix, Android, Oracle, Kubernetes, FreeBSD, Apache Kafka, New Relic, Linux, iOS


Technical Leadership, Logback, Openfire, Natural Language Processing (NLP), SOAP, Java 17, OpenTelemetry, Apache Cassandra, XMPP, Shell Commands, Hexagonal Architecture, NATS, TimescaleDB, Generative Pre-trained Transformers (GPT)

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