Sergei Udalov
Technical Lead · High-Scale Backend Systems · Ruby on Rails
sergei.udalov@gmail.com, https://t.me/SergeiUdalov, linkedin.com/in/sergeiudalov/
I have more than 20 years of experience building backend applications and, since 2017, leading developers and cross-functional teams comprising more than 20 engineers and analysts. I have worked on core e-commerce and fintech systems at Dixy, Samokat, Megamarket, and Raiffeisen Bank.
My primary focus is the architecture, performance, and reliability of distributed systems, microservice integrations, technical debt management, and engineering process development. I have launched products and teams from scratch, mentored engineers, and improved the performance of critical workflows by up to 10x.
What I do:
- Design and evolve high-load backend systems
- Improve service performance, reliability, and observability
- Drive architectural decisions and manage technical debt
- Grow teams and improve engineering processes
Technical Focus: Ruby, Ruby on Rails, PostgreSQL, ClickHouse, Kafka, Redis, microservices and event-driven architecture, DDD, C4, Docker, Kubernetes, GitLab CI/CD, OpenTelemetry, Jaeger
Public Speaking & Community Contributions
- RubyRussia 2023/2024/2025 — architecture, test automation, database migrations
- TechLead Conf 2025 — software architecture
- SberMarket RubyMeetup 2023 — writing automated tests with RSpec (speaker)
- Internal seminars at Balance Platform — code review practices, architectural development (host)
- HeavyTech podcast host — discussions of trends, architectural patterns, and leadership in IT
- Creator of technical content on YouTube and Telegram — promoting modern approaches
- GeekBrains expert & course instructor — contemporary practices and trends in software development
- Other meetups and community contributions
Experience
Lead Backend Engineer
Dixy | November 2025 - Present
Develop core backend components and integrations for the Dixy mobile app as part of its systems engineering team. Drive cross-cutting architectural changes, performance optimization, and improvements to development and delivery processes.
Achievements:
- Improved inventory synchronization performance by 10x, reducing execution time to two minutes through a migration from ClickHouse to PostgreSQL, batch integration with API Hub, and parallel incremental data processing
- Changed GitLab CI pipelines from sequential to parallel execution, reducing bottlenecks between developers
- Built DevContainers and supporting scripts to standardize project setup and streamline developer onboarding
- Established consistent code review criteria that distinguish required changes from recommendations
- Implemented an adapter layer for routing notifications across Telegram, Mattermost, and other channels
Key Skills: Ruby, Ruby on Rails, PostgreSQL, ClickHouse, Apache Kafka, Redis, Docker, Kubernetes, S3, GitLab CI/CD, Microservices Architecture, Software Architecture, Backend Development, API Integration, Performance Optimization, Parallel Data Processing, Code Review
Technical Lead
Raiffeisen Bank | July 2025 - September 2025
Led technical development across three cross-functional teams comprising more than 20 engineers and analysts within a single unit. Owned architectural decisions, the technical roadmap and backlog, technical debt management, and employee development.
Achievements:
- Updated C4 architecture diagrams for three products, closing documentation gaps and creating a coherent architectural view
- Established a unified approach to technical roadmapping across three teams
- Introduced a new technical debt management process
- Oversaw the migration of one product to new infrastructure, bringing the initiative to 80% completion during my tenure
- Established a regular one-on-one process with team members
- Prepared the promotion case and initiated a promotion for a team member
- Presented a talk on database migrations at RubyRussia 2025
Key Skills: Technical Leadership, Multi-Team Leadership, Employee Development, Software Architecture, Microservices Architecture, C4, Technical Roadmapping, Technical Debt Management, Observability, OpenTelemetry, Jaeger, Kubernetes, GitLab CI/CD, Java, Kotlin, Apache Kafka, PostgreSQL, Jira, Technical Documentation Automation
Product Team Lead
Samokat.tech (ecom.tech) | April 2023 - June 2025
Led three development teams comprising more than 18 developers, building scalable e-commerce solutions. Owned architectural decisions, code reviews, hiring, and team development.
Achievements:
- Successfully launched 3 new products to production
- Formed development team from scratch
- Implemented Domain-Driven Design (DDD) architectural approach
- Established end-to-end development processes for new teams
- Implemented technical debt management processes
- Mentored 5 developers for promotions, including preparing a successor team lead
- Presented talks at RubyRussia 2023/2024 and TechLead Conf 2025
Key Skills: Team Leadership, Public Speaking, Ruby, PostgreSQL, Apache Kafka, Back-End Web Development, Ruby on Rails, RSpec, Software Architecture, Unified Modeling Language (UML), Interviewing, Test Automation, Continuous Integration (CI), Redis, Docker, SQL, Git, Jira, Object-Oriented Programming (OOP), GraphQL, RESTful WebServices
Ruby Practice Lead
Balance Platform | October 2021 - April 2023
Established best practices, architectural standards, and team development processes across Ruby development teams. Developed new “Core” library to increase maintainability of software solutions
Achievements:
- Implemented comprehensive candidate evaluation system
- Designed RPC protocol for internal services
- Created code review guidelines and standards
- Developed core application framework
- Built competency matrix for Ruby developers
- Conducted 10+ internal seminars and public Ruby meetup presentations
- Enhanced architectural committee processes
Team Lead
Balance Platform | August 2020 - August 2021
Managed development team of 9 developers, implementing processes from design to delivery, code reviews, hiring, and team development.
Achievements:
- Achieved significant increase in system throughput
- Improved system stability and reliability
- Streamlined release build processes
- Enhanced Jira workflow discipline
- Implemented on-call rotation process
- Introduced Product Backlog Refinement (PBR) process
- Built analytics module using ClickHouse
- Prepared team lead successor
Key Skills: Team Leadership, Software Architecture, ClickHouse, PostgreSQL, RabbitMQ, Public Speaking, Unified Modeling Language (UML), Docker, Kubernetes, Jira
Senior Developer
Balance Platform | September 2019 - August 2020
Developed Lending-as-a-Service (LaaS) solutions and internal microservices for credit automation systems.
Achievements:
- Optimized core system performance
- Improved SQL query efficiency
- Developed business event collection service for analytics
- Led monolith refactoring (service extraction)
- Enhanced LaaS service functionality
Key Skills: Ruby, ClickHouse, Gitlab, Continuous Integration (CI), PostgreSQL, Docker, Object-Oriented Programming (OOP)
Team Lead
Soft Telematics | June 2017 - August 2019
Coordinated development team of 7 developers working on “Platon”, “Obоz”, and “Kospro toll roads” projects.
Achievements:
- Mentored 3 developers from middle/senior level to team lead positions
- Developed multiple admin interfaces for “Kospro toll roads” payment system
- Implemented automated testing across several “Platon” modules
- Enhanced mobile application APIs
- Added comprehensive reporting features for “Platon”
- Significantly expanded “Obоz” functionality (document management for freight transportation system)
Key Skills: Team Leadership, Ruby on Rails, RabbitMQ, Camunda BPM, Microservices, ClickHouse, Docker Swarm, Keycloak, Ruby, Java, Python
Senior Ruby Developer
Soft Telematics | April 2017 - June 2017
Enhancement of “Platon” toll collection system
Achievements:
- Developed report generation service
- Fixed and configured broken automated tests
- Set up automated test execution pipeline
- Implemented test database build and deployment, enabling reliable test runs
Key Skills: Ruby, PostgreSQL, RabbitMQ, Back-End Web Development, Ruby on Rails, RSpec, Test Automation, Continuous Integration (CI), Redis, Docker, SQL, Jira, Object-Oriented Programming (OOP), RESTful WebServices
Ruby Developer
Source[Lab] | December 2015 - April 2017
Development of web applications for various UK companies (outsourcing).
Achievements:
- Developed document management system for ORAC service for accounting assistance provided to disabled students
- Integration of Idibu (CV advertising) with Hiring Hub service (HR service)
- Implemented beach rating algorithm (kite surfing) by wind direction and strength for Geroush service
- Several applications migrated from vendor-locked services Github/Codeship/Heroku to open solutions Gitlab/Gitlab CI/Dokku. Docker was used for CI
Key Skills: Ruby, PostgreSQL, Back-End Web Development, Ruby on Rails, RSpec, Interviewing, Test Automation, Continuous Integration (CI), Redis, SQL, Git, Object-Oriented Programming (OOP), RESTful WebServices
Ruby Developer
SeoPult | March 2014 - December 2015
Development of backend services and API solutions for SEO platform.
Achievements:
- Speedup of generating json/xml/text to provide quick API response time
- Backend core service for internal use: workers based on Sidekiq, remote RPC access, RESTful API
- Frontend integration of QIWI payment system
- Working on highloaded HTTP crawler written in Go language with RPC access
Key Skills: Ruby, Ruby on Rails, Go, Sidekiq, RPC, PostgreSQL, TDD, Ajax, JavaScript, Capistrano, Git, Back-End Web Development, RSpec, Test Automation, Redis, SQL, Object-Oriented Programming (OOP), RESTful WebServices
Ruby Developer
Social Quantum | October 2012 - March 2014
Development of backend for high-load SEO services
Achievements:
- Implementing automated pricing tool (project core)
- Modifications of RPC API of core system
- Rewritten a number of PGQ workers to use new internal API
- Payment gateway via QIWI system using RESTful API
- Financial reports generators
Key Skills: Ruby, Ruby on Rails, PostgreSQL, TDD, PGQ, Ajax, JavaScript, RPC, REST, Memcache, Capistrano, Git, Back-End Web Development, RSpec, Test Automation, SQL, Object-Oriented Programming (OOP), RESTful WebServices
Ruby Developer
Undev.ru | August 2011 - October 2012
Development of web applications and payment gateway integrations.
Achievements:
- Developed an internal API service for payment acceptance, integrating PayPal, PerfectMoney, and other payment systems
- Built an e-commerce website for VPN provider Ivacy
- Developed an embedded concurrent application for managing playlists on TV set-top boxes
- Automated financial reporting for Ivacy using Google Analytics
Key Skills: Ruby, Ruby on Rails, E-Payments, MsSQL, Ajax, JavaScript, Celluloid, TDD, Memcache, Background Jobs, Capistrano, Git, Back-End Web Development, RSpec, Test Automation, SQL, Object-Oriented Programming (OOP), RESTful WebServices
Ruby Developer
June Marketing | December 2009 - August 2011
Development of websites on Ruby on Rails, PHP website modifications, Linux server administration.
Achievements:
- Developed more than 10 e-commerce websites
- Developed CMS based on Ruby on Rails, allowing creation of new “content” types on the fly
- Set up automated backup system with encryption
- Set up monitoring system for running processes
Key Skills: Ruby, Ruby on Rails, JavaScript, jQuery, Ajax, RESTful, JSON, Git, RSpec, Capistrano, Background Jobs, PostgreSQL, Caching, Shell-scripting, Monit, PHP, MySQL, Selenium
PHP Developer
HROS Booking System | November 2008 - December 2009
Development of online hotel booking system.
Achievements:
- Developed and implemented 2 online booking systems through partner services Travco and Pegasus
Key Skills: PHP, Symfony, XML, JavaScript, jQuery, Ajax, MySQL, Git, Subversion, Capistrano
Ruby Developer
Sportweek | December 2007 - October 2008
Development of news portal and server administration.
Achievements:
- Developed sports news resource (more than 10 news writers)
- Developed system of online text broadcasts with ajax-chat function for guests
- Implemented animated photo gallery
- Configured Linux server with Passenger and automated deployment using Capistrano
Key Skills: Ruby on Rails, JavaScript, Ajax, Prototype, Subversion, PostgreSQL, Linux, Capistrano, Passenger
PHP Developer
High-Web | February 2007 - November 2007
Development of online services.
Achievements:
- Development of hotel booking system with integration through Travco (not completed)
Key Skills: PHP, PHPUnit, Symfony, XML, API, Subversion
Developer Intern
Russian Tennis Federation | February 2006 - November 2006
Websites modification and development of new web services.
Achievements:
- Developed tennis players rating service
- Developed news system
- Developed web client for email work
- Developed Q&A service (forum phpbb-like service)
Key Skills: PHP, PHP4A, JavaScript, HTML, MySQL, MSSQL, Access, SSH, IMAP
Skills
Programming Languages
Ruby, Go, JavaScript, Kotlin, Java, SQL, Python
Frameworks & Libraries
Ruby on Rails, RSpec, GraphQL, Sinatra, Hanami, Spring Boot, Symfony, Prototype, jQuery, Ajax
Databases
PostgreSQL, ClickHouse, Redis, MySQL, SQLite, MongoDB, MSSQL, Access
Testing & Quality
RSpec, Capybara, Cucumber, Selenium, PHPUnit, CI/CD, TDD, Test Automation
DevOps & Infrastructure
Docker, Kubernetes, GitLab CI, GitHub Actions, Kafka, RabbitMQ, Prometheus, Grafana, ELK Stack, Subversion, Git, Capistrano, Linux, Redis, Passenger
Architecture & Design
Microservices Architecture, Event Streaming, REST API, GraphQL, Domain-Driven Design (DDD), Unified Modeling Language (UML), Clean Architecture, CI tools
Project Management & Team Leadership
Agile, Scrum, Jira, Team Leadership, Interviewing, Code Review, Technical Mentoring, Team Building, Process Improvement
Education
Moscow Aviation Institute (National Research University), 2008
Five-year Specialist degree in Applied Mathematics and Physics (comparable to a Master’s degree)
Qualification: Mathematician, Systems Programmer
Contact Information
- Email: sergei.udalov@gmail.com
- Telegram: @SergeiUdalov
- LinkedIn: linkedin.com/in/sergeiudalov
- GitHub: github.com/sergio-fry
- YouTube: youtube.com/@SergeiUdalov
- Location: Moscow, Russia