Yaroslav Kolomiiets:
Full Stack Engineer, 8 years of experience

Contact information

Email: kolomiiets.y.n@gmail.com

Socials: LinkedIn

About me

Adept of maintainable and simple (but not simpler than necessary) solutions for challenging problems.
I'm actively seeking a project that aims to make a positive impact on the world, whether in a big or small way.

Techologies and skills

Worked closely with:

Used at work:

Tinkering with:

Experience

Intergiro, Warsaw, Poland

Key technologies: Node.js, React, Javascript/Typescript, Express, NestJS, MySQL, PostgreSQL, SQLite, Docker, Kubernetes, Terraform, Teamcity, Google Cloud Platform, Cloudflare Workers

During my 3-year tenure at Intergiro, I progressed from a individual contributor to a team leader, working across the entire product development lifecycle. I collaborated closely with cross-functional teams to design, develop, test, and deploy critical features; consistently drove technical improvements, fostered team growth through mentoring, and maintained a strong focus on delivering business value.

Lead Software Engineer, PSP and Merchant Acquirer Team

April 2023 - June 2024

  • I was deployed to resolve urgent issues in the Acquiring Team's revenue-critical product.
  • Led a team of 5 to stabilize a newly acquired product, enabling the company to scale its transactional throughput by 10x; the product became the primary revenue generator, contributing 80% of total revenue
  • Eliminated data loss and significantly boosted query performance by migrating (without any downtime) both historical and ongoing data from Cloudflare Workers KV storage and Durable Objects to PostgreSQL
  • Migrated critical project components - including settlement and reconciliation of transactions, payouts, and balance calculation - to the company’s technological stack, enhancing system performance, reliability, and observability while enabling faster development of new features
  • Shared best practices with my team, fostering a culture of continuous improvement. Onboarded a new team member, guiding them in both technical and domain-specific aspects of the project.

Senior Software Engineer, Onboarding and Internal Tools Team

September 2021 - March 2023

  • Designed and documented a PSD2-compliant solution for SCA and dynamic linking, and coordinated its implementation across 4 teams to ensure seamless integration spanning multiple microservices and frontends
  • Developed the core of automated corporate and individual KYC flows, leading to a 44% reduction in customer onboarding costs and enabling the straightforward expansion of these flows in the future
  • Led a team of 4 in developing a new B2B onboarding portal (web application facing both customers and onboarding staff), meeting a critical deadline and increasing the conversion rate by 30%
  • Wrote integrations with 10+ different 3rd party services, including Twilio, Onfido, Hubspot, and others
  • Developed multiple packages and developer tools improving developer experience and minimizing manual activities
  • Optimized the asynchronous communication layer between services, enhancing reliability and scalability across the organization.
  • Collaborated with QA to improve end-to-end test implementations, ensuring smoother and more reliable releases.
  • Interviewed, onboarded, and mentored developers, fostering their independence and supporting their growth within the team through pair programming and knowledge-sharing sessions

Software Engineer, Onboarding Team

April 2021 - August 2021

  • Standardized API error responses across all endpoints and developed a testing utility to simplify writing integration tests for API endpoints using the Chai plugin
  • Refactored a React application, enabling it to be efficiently split into smaller bundles

ARTADIAN GAMING LLP, Kyiv, Ukraine

Key technologies: Node.js, Javascript/Typescript, Express, MongoDB, Docker, Docker Compose, Unity/C#, React, git, bash scripts

Lead Software Engineer

February 2017 - December 2020

  • Led development of a cross-platform (iOS and Android) mobile multiplayer game, growing the player base from 0 to over 500,000 players within three years
  • Participated in discussions on new feature development and took a leading role in designing and implementing them, ensuring alignment with both technical and user experience goals
  • Managed and optimized a Node.js monolith backend that had been using legacy niche framework, leading a gradual migration to Express.js, containerization with Docker/Docker Compose, and splitting the monolith into fine-grained services for improved scalability and maintainability
  • Developed and deployed the application to a dedicated Linux server, while actively monitoring and ensuring the health of both development and production environments, promptly identifying and resolving any production issues
  • Designed and maintained a MongoDB database, managing performance and data integrity across multiple environments
  • Oversaw creation of an internal React-based web application for content creators to streamline quiz content management
  • Directed the transition from an iOS-exclusive Objective-C codebase to a Unity/C# cross-platform application, expanding to Android and experimenting with a web version
  • Collaborated closely with client-side engineers on critical tasks, including networking architecture, performance optimization, integration with third-party services, and complex feature development
  • Developed utilities for asset compression and management and streamlined build and deployment pipelines for App Store and Google Play releases
  • Engaged with end-users to address feedback and improve the overall player experience

Education and certification

AWS Certified Solutions Architect - Associate

February 2025

Bachelor's Degree: Software Engineering

September 2015 - May 2019

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

42 system: Software Engineering

September 2016 - December 2018

UNIT Factory - Kyiv, Ukraine