Evgeniy Demin, Developer in Belgrade, Serbia
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Evgeniy Demin

Verified Expert  in Engineering

Back-end Developer

Belgrade, Serbia
Toptal Member Since
April 24, 2023

Evgeniy is a passionate and dedicated product builder. He prioritizes users' satisfaction and product quality, striving to achieve the best outcomes at the lowest cost while embracing challenges as opportunities for growth. He has authored several open-source projects and contributed to many more, recognizing the importance of having the proper tooling to build robust and high-quality software.



Preferred Environment


The most amazing...

...thing I've done is help engineers build great products by authoring open-source projects, enabling them to create robust, high-quality software.

Work Experience

Principal Back-end Engineer

2018 - 2023
  • Acted as a principal engineer, suggesting process improvements that increased productivity for the entire team. I proactively identified potential issues and stepped in to help resolve them, creating an atmosphere of clarity and collaboration.
  • Contributed to open-source projects and published three of them—n1_loader, factory_trace, and database_consistency, which helped engineers and companies avoid potential issues and increase productivity.
  • Participated in several company-wide initiatives, such as standardizing front-end to back-end communication and service-oriented architecture migration.
Technologies: Ruby

Back-end Developer

2017 - 2018
Lumar (formerly Deepcrawl)
  • Built an automated API documentation tool with OpenAPI support, which was accepted and integrated into the company's technical stack. The tool saves time and effort for developers and has been shared with the OpenSource community.
  • Served as the only remote contractor at Lunar and performed at a high level, demonstrating the ability to work productively and effectively in a remote environment.
  • Helped the Lunar team with optimizations and implementing new features, showcasing versatility as a software engineer and contributing to the continued success of the company.
Technologies: Ruby, Ruby on Rails (RoR), PostgreSQL, MySQL

Back-end Developer

2016 - 2017
  • Synchronized users' music collections with Apple Music, which enhanced the user experience and allowed for seamless integration with the popular music streaming platform.
  • Developed and implemented a recommendation algorithm that helped users discover new music and connect with friends with similar music tastes, contributing to the success of the MuzApp mobile application.
  • Optimized complex SQL queries and wrote new API endpoints, improving the performance and functionality of the application and enhancing the overall user experience.
Technologies: Ruby, PostgreSQL

Back-end Developer

2016 - 2016
  • Migrated the legacy code to modern versions, ensuring that the application was up to date and functioning optimally, which helped maintain the platform's reliability and stability.
  • Implemented new features, such as call tracking and conversion analytics, contributing to the company's growth and success and showcasing technical proficiency and problem-solving skills.
  • Covered existing functionality with unit tests, helping ensure that the application was bug-free and reliable and that any new changes or updates were tested thoroughly before deployment.
Technologies: Ruby, Ruby on Rails (RoR), PostgreSQL

Back-end Developer

2016 - 2016
  • Designed and implemented the functionality for a new game, contributing to the project's success and showcasing technical expertise and problem-solving skills.
  • Communicated with stakeholders effectively, ensuring that project requirements were understood and any issues were addressed promptly and professionally.
  • Reviewed teammates' work, providing constructive feedback and ensuring the project met quality standards and was delivered on time and within budget.
Technologies: Ruby, Ruby on Rails (RoR), PostgreSQL

Talent Portal for Toptal

As a back-end engineer on a Ruby on Rails project with GraphQL API, I was in charge of designing and implementing the server-side logic of the application. I managed the database, handled data validation and authentication, and created GraphQL queries and mutations.

In addition, I optimized the performance of the API, troubleshot issues, and collaborated with front-end developers to integrate the API with the user interface. Writing automated tests to ensure the quality and reliability of the codebase was also part of my job. Overall, I was fully involved in the project's development and worked to ensure its success.




RubyMine, Git


Ruby on Rails (RoR)


Ruby, GraphQL, Bash


Elasticsearch, PostgreSQL, Redis, MySQL

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