Sergey is available for hire

Sergey Moiseev

Verified Expert in Engineering

Full-stack Developer

Tallinn, Estonia

Toptal member since May 9, 2014

Expertise

Full-stack PostgreSQL CSS Ruby on Rails Ruby REST API Docker Angular SQL MySQL JavaScript Linux Nginx UML

Bio

Sergey is a proficient full-stack software engineer who has worked on intricate web projects. He possesses strong analytical abilities and excels in gathering project requirements. Sergey's experience ranges from being a full-stack developer to a team lead/CTO.

Portfolio

Mightycause Corporation

Ruby on Rails (RoR), MySQL, REST APIs, Angular, JavaScript, Pundit, Rolify

American Technological Research and Consulting Firm

Ruby on Rails (RoR), SQL, Apache Kafka, Oracle

Giftly Inc

SQL, Ruby on Rails (RoR), JSON, APIs, eCommerce, Legacy Code, Third-party APIs...

Experience

PostgreSQL - 20 years
Ruby on Rails (RoR) - 16 years
RESTful Web Services - 15 years
JavaScript - 15 years
Docker - 7 years
Angular - 5 years
Turbo - 2 years
Hotwire - 2 years

Availability

Full-time

Preferred Environment

Angular, Ruby on Rails (RoR), Ruby, Turbo

The most amazing...

...things I've accomplished is performing migrations for diverse projects to newer frameworks and architectures, resulting in a quicker response to business needs.

Work Experience

Senior Back-end Developer (Ruby on Rails)

2024 - 2025

Mightycause Corporation

Architected and implemented a Pundit/Rolify-based authorization system, replacing legacy Aegis framework across 50+ controllers while maintaining backward compatibility through feature flags with zero downtime.
Developed hierarchical role-based access control with 30+ policy classes, reducing code duplication and enabling granular permissions for multi-tenant application architecture.
Optimized database queries in permission checks, eliminating N+1 issues and improving application performance through efficient query construction and caching.
Established self-hosted GitHub CI workflow with parallel test execution, reducing test suite runtime, and implementing comprehensive code coverage reporting.
Implemented external data import system with ActiveStorage, enabling automated synchronization from multiple government sources with proper error handling and retry mechanisms.
Enhanced code quality through Rubocop and Brakeman, addressing 100+ code style issues and security vulnerabilities with automated correction capabilities.

Technologies: Ruby on Rails (RoR), MySQL, REST APIs, Angular, JavaScript, Pundit, Rolify

Ruby on Rails Engineer

2023 - 2023

American Technological Research and Consulting Firm

Completed merge of two key projects into the single Rails repository reducing the complexity of development workflows and removing 40+ duplicated models and specs for those.
Implemented Thor-based CLI for code-generation of custom migrations for Oracle datastore according to the business-specific requirements for change-control in organization-span database.
Took part in migrating project data streams from database storage to Kafka topic.

Technologies: Ruby on Rails (RoR), SQL, Apache Kafka, Oracle

Back-end Developer

2022 - 2023

Giftly Inc

Developed the back end for the new corporate portal. Implementation wraps the legacy layer codebase and extends it for the needs of new business processes without changing how the same legacy layer provides services to different consumer components.
Implemented full test coverage for that work as well as needed missing coverage of key legacy components.
Helped with UI/UX review process of new portal development for an online gifts platform.

Technologies: SQL, Ruby on Rails (RoR), JSON, APIs, eCommerce, Legacy Code, Third-party APIs, CSS, HTML, API Integration, Payment APIs, Sidekiq, State Machines, Stripe API, RSpec, Redis, Linux, Git, JavaScript, SQL-99, Devise, REST APIs, UML

Front-end Developer

2020 - 2023

Scionian

Supported the development of the Ask Ari mobile application. Released multiple versions of the application to both the App Store and Google Play market.
Supported the development of the web-based version of Ask Ari.
Built a new version of Ask Ari on top of Angular, NgRx, and the Ionic framework in the format of an NX-based monorepo for reducing code duplication.

Technologies: JavaScript, HTML, CSS, Angular, Redux, Expo, Firebase, Ionic 3

Senior Full-stack Developer (Independent Contract)

2020 - 2023

International Technological University

Developed and launched My.itu.edu, an Angular and NgRx-based platform for students to register and pay for courses at university.
Implemented the back end for My.itu.edu on top of a Ruby on Rails-based SRM platform. The solution included the management of scholarship discounts, prepaid nugget course implementation, and reporting for students and account payable representatives.
Implemented the migration process for legacy data to provide continued operations for the teaching process.
Migrated the old AngularJS-based SRM admissions interface to a Turbo-based interface that allowed delivering new features way faster and more efficiently.
Migrated the My.itu.edu Angular and NgRx-based interface into a Turbo-based SRM platform, reducing code duplication and providing a full-cycle student experience from admission to graduation.
Implemented a Turbo-based UI for Angular Material web components using Stimulus with support for complex UI elements like autocomplete and chipset with limited and Typeahead server-based lists.
Implemented Elixir/Phoenix Live View-based internal chat platform for ITU students and staff.

Technologies: Ruby on Rails (RoR), Angular, NgRx, Turbo, Stimulus, Elixir, Phoenix, Phoenix LiveView

Full-stack Developer

2018 - 2022

Ygrene Energy Fund

Aided in creating a new prequalification and application process with Angular 6 and NgRx.
Helped create a monorepo layout for Angular apps, using Nx, NgRx, shared modules, and environment to deliver new front-end projects quickly and efficiently.
Created a supporting proxy-like module for a new application process back end to provide new workflows in an existing feature-flag-based process without additional data models using Ruby on Rails (RoR).
Supported an automated underwriting system implementation by covering all key Ruby code, making it reliable and maintainable.
Implemented the initial message bus encryption mechanism for securing microservice interoperation using Ruby and AWS SQS.
Migrated multiple services from Scala to RoR, using Scala code as a source of requirements. They include external postal providers, environment management solutions like backup scrubbing and event-based S3 archival solutions, and GIS-based solutions.
Helped maintain and improve automatic microservice client generation, using the zero-rails_openapi gem and open API generator.
Built a new system area configuration service using a Hotwire (Turbo) Ruby on Rails 7 architecture.

Technologies: Amazon Web Services (AWS), Redux, RESTful Web Services, Angular Material, NgRx, Swagger, Docker, Scala, Kubernetes, Ruby on Rails (RoR), Ruby, Angular, SAML, Turbo, Hotwire, Material Design, TypeScript, Ruby on Rails 7, Tailwind CSS, Stimulus, CSS, HTML, API Integration, Third-party APIs, Legacy Code, Sidekiq, NGINX, State Machines, Protractor, RSpec, Redis, MySQL, Linux, Git, JavaScript, SQL-99, Devise, REST APIs, Sass, UML

Full-stack Web Developer

2017 - 2018

Caspar Health

Created a front-end application for the main business platform utilizing Angular 5 and NgRx.
Helped release a product that made one of five finalists at Disrupt Berlin Startup Battlefield 2017.
Aided in refactoring and developing the Ruby on Rails application back end.

Technologies: Amazon Web Services (AWS), Ruby on Rails 5, Redux, RESTful Web Services, Angular Material, NgRx, Docker, PostgreSQL, Angular, CSS, HTML, API Integration, Third-party APIs, Sidekiq, NGINX, State Machines, RSpec, Redis, Linux, Git, JavaScript, SQL-99, Devise, REST APIs, Sass, UML

Full-stack Web Developer

2017 - 2017

Everwill

Set up and moved an AWS Elastic Beanstalk Multicontainer Docker configuration to production.
Built a new version of the company's main application on Angular 4.
Implemented a flexible workflow engine for the application.

Technologies: Redux, RESTful Web Services, NgRx, Docker, MongoDB, Ruby on Rails (RoR), Ruby, Angular, CSS, HTML, Third-party APIs, Linux, Git, JavaScript, SQL-99, Sass

Full-stack Web Developer

2014 - 2017

International Technological University

Implemented ITU Bridge, a project to help students and alums to apply for jobs at top companies.
Implemented ITU's single sign-on solution, the ITU ID.
Implemented ITU Student Relationship Management, a system for automating an admissions data and document collection process. The system included Stripe and SalesForce integrations.
Worked as a back-end Rails developer, an AngularJS front-end developer, and DevOps for all mentioned projects.

Technologies: Ruby on Rails 5, Redux, RESTful Web Services, Angular Material, MySQL, CSS3, HTML5, Ruby on Rails (RoR), Ruby, CSS, HTML, API Integration, Third-party APIs, Payment APIs, Sidekiq, NGINX, State Machines, AngularUI, Salesforce API, Stripe API, RSpec, Redis, Linux, Git, JavaScript, SQL-99, Devise, REST APIs, Sass, UML

CTO

2013 - 2014

Information Ideas

Implemented a production-ready SPA job search site.
Formed a team of two developers to work on a project.
Built a set of AngularJS directives for competence tree rendering and selection.
Created a competence search engine on top of Redis.
Created a complex UI with interacting controls on top of AngularJS.

Technologies: Ruby on Rails 5, RESTful Web Services, Redis, PostgreSQL, Ruby on Rails (RoR), CSS, HTML, API Integration, Third-party APIs, RSpec, Linux, Git, JavaScript, SQL-99, Devise, REST APIs, Sass, UML

Development Team Lead

2012 - 2013

HeadHunter Group

Implemented an online competence-based candidate search project in a small team of three developers.
Provided a full cycle of requirements analysis for the project.
Implemented property search on top of a Redis set intersection.
Built a RIA interface for a project using Backbone.js.
Created an automated competence pre-fill solution using candidate resumes as the data source.

Technologies: RESTful Web Services, Backbone.js, Redis, PostgreSQL, Ruby on Rails (RoR), CSS, HTML, API Integration, Third-party APIs, Sidekiq, State Machines, RSpec, Linux, Git, JavaScript, SQL-99, Devise, REST APIs, Sass, UML

CTO

2011 - 2012

KupiKupon Global

Supported a high-load production environment for a daily deal site on top of Drupal.
Managed and implemented a new version of a site using Ruby on Rails.
Migrated all data to a new project and replaced the old project with the new one.
Formed a development team of ten developers by putting together position requirements, interviewing, and training.
Implemented a VoIP call center solution based on Asterisk PBX.

Technologies: RESTful Web Services, PostgreSQL, Ruby on Rails (RoR), CSS, HTML, API Integration, Third-party APIs, Legacy Code, Payment APIs, Sidekiq, NGINX, State Machines, RSpec, Redis, Linux, Git, JavaScript, SQL-99, Devise, REST APIs, Sass, UML

CTO

2008 - 2011

Digital Distribution Center

Formed a team and started an internal software development process in the company.
Moved an outsourced project with the support of a formed team and completed its development from early prototype to production-ready version.
Managed a complete rewrite of the project from PHP to Ruby on Rails.
Created an in-house digital right management solution for the project.
Applied Agile practices to the working process and set up a development cycle for the company.

Technologies: RESTful Web Services, VMware, Flex, Flash, PHP, PostgreSQL, Ruby on Rails (RoR), CSS, HTML, API Integration, Third-party APIs, Legacy Code, Payment APIs, Sidekiq, NGINX, State Machines, RSpec, Redis, Linux, Git, JavaScript, SQL-99, Devise, REST APIs, Sass, UML

Lead Developer | System Analyst | Head of R&D

2004 - 2008

Chronopay B.V.

Implemented integrations with Parex (FirstData.lv), UCS (abgcard.ru), and other payment providers.
Developed many improvements to the Chronopay PSP system. Included many new architectural improvements, integration processing, 3D secure implementation, and more.
Applied Agile practices in the working process and set up the development cycle for the company.
Provided analytical support for the work cycle of the R&D department. Provided a full cycle of business analysis for the company.
Provided support for three annual PCI DSS certifications.

Technologies: Mono, PostgreSQL, PHP, CSS, HTML, API Integration, Third-party APIs, Legacy Code, Payment APIs, Linux, JavaScript, SQL-99, UML

Lead SW Developer

2000 - 2001

Ayaxi

Developed TenderOnline.ru (currently unavailable) from base technical requirements to the product in use.
Managed a team of three developers in the process of developing TenderOnline.ru.
Developed modules for the Ayaxi main product Ayaxi Publisher, used in client installations.
Provided development analysis for the early stages of the president of Russia website [www.kremlin.ru].
Developed methods for outsourcing work support, code format requirements, and documentation format guides.

Technologies: Microsoft SQL Server, Active Server Pages (ASP), CSS, HTML, JavaScript, SQL-99

Experience

Turbo Material Components

https://github.com/full-stack-biz/turbo_material

Turbo Material is a library providing drop-in support for Material Design Components in Hotwire-enabled Rails applications. It provides users with needed Stimulus.js controllers for implementing a Material Design look and feel on such components and complex behaviors on top of Turbo frames.

ITU.edu Student Relations Module

https://my.itu.edu/

A Ruby on Rails and Hotwire-based student relations platform for ITU.edu students and admissions office staff. It allows potential students to apply to university, students to apply for the courses and payment installment plans, pay due fees, and plan their education.

Giftly Corporate Experience

https://www.giftly.com/corp

Ruby on Rails-based corporate user experience extending existing end-user flows with business-oriented scenarios.

As a back-end developer, I was involved in all stages of active development, from early prototyping to post-release improvements.

Education

1995 - 2001

Master's Degree in Computer Engineering

Moscow State Institute of Electronics and Mathematics (Technical University) - Moscow, Russia

Skills

Libraries/APIs

Devise, REST APIs, NgRx, Pundit, Stripe API, Salesforce API, Sidekiq, AngularUI, Restangular, Backbone.js, Authorize.net, Rolify

Tools

NGINX, Git, RSpec, Capistrano, Flash, VMware, Turbo, Hotwire, Expo

Languages

Ruby, HTML, CSS, UML, Sass, CSS3, HTML5, JavaScript, SQL-99, Active Server Pages (ASP), PHP, Scala, SAML, TypeScript, SQL, Elixir

Frameworks

Angular, Ruby on Rails (RoR), Angular Material, Slim, Swagger, Mono, Flex, Ruby on Rails 5, Protractor, Redux, Ruby on Rails 7, Tailwind CSS, Stimulus, Ionic 3, Phoenix, Adobe Flex, Material UI

Platforms

Docker, Linux, Amazon Web Services (AWS), Kubernetes, Firebase, Apache Kafka, Oracle

Storage

PostgreSQL, MySQL, Redis, Microsoft SQL Server, MongoDB, JSON

Other

State Machines, RESTful Web Services, API Integration, Payment APIs, Full-stack Development, Puma, ISO 8583, GitFlow, Material Design, APIs, eCommerce, Legacy Code, Third-party APIs, Software Development, Phoenix LiveView, Ruby Gems

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